Commit Graph

35204 Commits

Author SHA1 Message Date
danno
4447405b17 [builtins]: Uniformly push argument count in TF-generated builtins
Review-Url: https://codereview.chromium.org/2467513002
Cr-Commit-Position: refs/heads/master@{#40712}
2016-11-03 08:37:01 +00:00
dschuff
4d2659a706 v8gen.py: change file open mode from 'aw' to just 'a'
'a' and 'w' are mutually exclusive and just 'a' is what we actually
want. Linux doesn't care (it just takes the first one) but Windows
throws a ValueError.

R=machenbach@chromium.org
BUG=None

Review-Url: https://codereview.chromium.org/2467363002
Cr-Commit-Position: refs/heads/master@{#40711}
2016-11-02 22:04:05 +00:00
cbruni
fdf0b3ee7a Revert of [tools] Support custom script injection for callstats.py (patchset #1 id:1 of https://codereview.chromium.org/2455623002/ )
Reason for revert:
speculative revert to address regressions on cnn.com benchmark.

Original issue's description:
> [tools] Support custom script injection for callstats.py
>
> This is a poor-man's solution to trigger page interactions.
>
> BUG=

TBR=jochen@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=

Review-Url: https://codereview.chromium.org/2464053005
Cr-Commit-Position: refs/heads/master@{#40710}
2016-11-02 20:37:17 +00:00
alph
fdca1bb2da [profiler] Make certain Runtime Call Stats fields atomic.
Make RuntimeCallTimer::parent_ and RuntimeCallStats::current_timer_
fields atomic as they are accessed from the signal handler.

BUG=chromium:660428

Review-Url: https://codereview.chromium.org/2464973002
Cr-Commit-Position: refs/heads/master@{#40709}
2016-11-02 18:50:36 +00:00
ahaas
a3b77d560e [wasm] Fix br_table in the wasm interpreter to use varuint32.
The wasm interpreter crashed because it interpreted the table of
br_table as a table of uint8, but according to the spec it is a table of
varint32. Therefore the wasm interpreter misinterpreted 0x80 0x00 as 128
and not as 0, which caused a crash.

R=tizer@chromium.org
BUG=chromium:660262
TEST=cctest/test-run-wasm/RunWasmInterpreted_Regression_660262

Review-Url: https://codereview.chromium.org/2463063002
Cr-Commit-Position: refs/heads/master@{#40708}
2016-11-02 17:07:00 +00:00
yangguo
e3f2910da7 [heap] reorder empty scope info in the root list.
Apparently the previous clean up has regressed performance in some
cases. This is an attempt to recover these regressions.

R=ulan@chromium.org
BUG=chromium:661567

Review-Url: https://codereview.chromium.org/2471493003
Cr-Commit-Position: refs/heads/master@{#40707}
2016-11-02 15:19:51 +00:00
rmcilroy
0fbf7243c6 [Interpreter] Remove skips from mjsunit tests which now pass.
BUG=v8:4680

Review-Url: https://codereview.chromium.org/2469283002
Cr-Commit-Position: refs/heads/master@{#40706}
2016-11-02 14:47:11 +00:00
jochen
bf77741d43 Reland "Create internal fields on global proxy objects"
Original CL description:
> Create internal fields on global proxy objects
>
> BUG=v8:5588
> R=verwaest@chromium.org

BUG=v8:5588
TBR=verwaest@chromium.org

Review-Url: https://codereview.chromium.org/2472573004
Cr-Commit-Position: refs/heads/master@{#40705}
2016-11-02 14:40:31 +00:00
ulan
bb24b91f15 [heap] Invoke incremental marking step before allocation.
This ensures that the newly allocated object immediatly precedes the
linear allocation area, which is needed for allocation folding.

For more info see:
https://bugs.chromium.org/p/chromium/issues/detail?id=659165#c13

BUG=chromium:659165

Review-Url: https://codereview.chromium.org/2464393002
Cr-Commit-Position: refs/heads/master@{#40704}
2016-11-02 14:14:10 +00:00
verwaest
5a18685e08 Thread decls-list through Declaration using a ThreadedList
This reduces per-scope overhead from minimally 6 words to 2 words, with one additional pointer per entry, rather than an average of 2 per entry for larger-than-4 element lists. For temp zone parsed functions it additionally makes the declaration-list actually freeable.

This introduces ThreadedList to implement the details of dealing with such a list.

BUG=v8:5209

Review-Url: https://codereview.chromium.org/2457393003
Cr-Commit-Position: refs/heads/master@{#40703}
2016-11-02 14:08:47 +00:00
littledan
baf0ec31ec Allow immutable prototype templates to inherit
To enable the global object prototype chain to be frozen, all objects
in the chain need to be marked as immutable prototype exotic objects.
However, a bug in the previous implementation of immutable prototype
exotic objects left the check in place when initially setting up the
object, which made it impossible to allow inheritance chains. This
patch removes that mistaken check.

BUG=v8:5149

Review-Url: https://codereview.chromium.org/2449163004
Cr-Commit-Position: refs/heads/master@{#40702}
2016-11-02 13:59:25 +00:00
jkummerow
5ce9760672 Revert of [ic] Experiment: disable map-specific handler cache. (patchset #1 id:1 of https://codereview.chromium.org/2462973003/ )
Reason for revert:
Causes performance regressions (up to 10% on the "IC" bucket). :-(

Original issue's description:
> [ic] Experiment: disable map-specific handler cache.
>
> IC data handlers support most of the hot cases nowdays. Let's see if
> the map-specific code cache still help us to improve things.
>
> BUG=v8:5561

TBR=ishell@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=v8:5561

Review-Url: https://codereview.chromium.org/2474653002
Cr-Commit-Position: refs/heads/master@{#40701}
2016-11-02 13:50:06 +00:00
danno
9e2fd36c3b [stubs]: Support 1->2 byte copies in CopyStringCharacters
In the process, add a more general mechanism for passing around
and amending list of CodeStubAssembler Variables. That change
makes it possible to more easily add Variables to loops that are
generated by utility functions, e.g. BuildFastLoop.

LOG=N

Review-Url: https://codereview.chromium.org/2461363002
Cr-Commit-Position: refs/heads/master@{#40700}
2016-11-02 13:19:27 +00:00
danno
fe552636be [turbofan] Support variable size argument removal in TF-generated functions
This is preparation for using TF to create builtins that handle variable number of
arguments and have to remove these arguments dynamically from the stack upon
return.

The gist of the changes:
- Added a second argument to the Return node which specifies the number of stack
  slots to pop upon return in addition to those specified by the Linkage of the
  compiled function.
- Removed Tail -> Non-Tail fallback in the instruction selector. Since TF now should
  handles all tail-call cases except where the return value type differs, this fallback
  was not really useful and in fact caused unexpected behavior with variable
  sized argument popping, since it wasn't possible to materialize a Return node
  with the right pop count from the TailCall without additional context.
- Modified existing Return generation to pass a constant zero as the additional
  pop argument since the variable pop functionality

LOG=N

Review-Url: https://codereview.chromium.org/2446543002
Cr-Commit-Position: refs/heads/master@{#40699}
2016-11-02 13:15:57 +00:00
mlippautz
588641f242 [heap] Fix Unmapper::TearDown to include delayed chunks
Delayed chunks in the unmapper are chunks that should be unmapped but could
potentially still be accessed by the sweeper (page header), hence their
unmapping is delayed.

During TearDown, however, we need to properly unmap those pages, i.e., check
that they can now be unmapped (should always hold) and properly unmap them.

BUG=chromium:656537
R=ulan@chromium.org

Review-Url: https://codereview.chromium.org/2472573003
Cr-Commit-Position: refs/heads/master@{#40698}
2016-11-02 13:10:38 +00:00
rmcilroy
ea5d4c1525 [Interpreter] Remove unused --ignition-eager flag.
BUG=v8:4280

Review-Url: https://codereview.chromium.org/2463353002
Cr-Commit-Position: refs/heads/master@{#40697}
2016-11-02 11:17:48 +00:00
bbudge
d2c3ae774d [Turbofan] Make fixed live ranges all double when aliasing is simple.
Only ARM should have fixed live range arrays for float / simd128.

LOG=N
BUG=v8:4124

Review-Url: https://codereview.chromium.org/2471533002
Cr-Commit-Position: refs/heads/master@{#40696}
2016-11-02 09:54:36 +00:00
bmeurer
3f3bacc319 [turbofan] Assign proper types to Parameter nodes.
R=epertoso@chromium.org

Review-Url: https://codereview.chromium.org/2223873002
Cr-Commit-Position: refs/heads/master@{#40695}
2016-11-02 09:34:08 +00:00
neis
24b1c1abfc [modules] Add namespace import snippet to test-bytecode-generator.
R=rmcilroy@chromium.org
BUG=v8:1569

Review-Url: https://codereview.chromium.org/2460403002
Cr-Commit-Position: refs/heads/master@{#40694}
2016-11-02 09:30:42 +00:00
Michael Achenbach
2bac8f8ce8 Whitespace change to trigger bots.
Cr-Commit-Position: refs/heads/master@{#40693}
2016-11-02 08:35:32 +00:00
zhengxing.li
3ef54ed693 X87: [compiler] Sanitize IC counts for vector based ICs.
port 5ef1bddf80 (r40690)

  original commit message:
  All vector ICs use the TypeFeedbackVector::ComputeCounts method now,
  while the remaining patching ICs still use the traditional way of
  counting on the TypeFeedbackInfo hanging off the fullcodegen code
  object. This fixes the problem that counts were sometimes off.

BUG=

  Drive-by-fix: Move FullCodeGenerator::CallIC to fullcodegen.cc.
Review-Url: https://codereview.chromium.org/2470063002

Cr-Commit-Position: refs/heads/master@{#40692}
2016-11-02 07:51:37 +00:00
machenbach
c61902e072 Revert of [turbofan] Support variable size argument popping in TF-generated functions (patchset #13 id:240001 of https://codereview.chromium.org/2446543002/ )
Reason for revert:
Seems to break arm64 sim debug and blocks roll:
https://build.chromium.org/p/client.v8.ports/builders/V8%20Linux%20-%20arm64%20-%20sim%20-%20debug/builds/3294

Original issue's description:
> [turbofan] Support variable size argument removal in TF-generated functions
>
> This is preparation for using TF to create builtins that handle variable number of
> arguments and have to remove these arguments dynamically from the stack upon
> return.
>
> The gist of the changes:
> - Added a second argument to the Return node which specifies the number of stack
>   slots to pop upon return in addition to those specified by the Linkage of the
>   compiled function.
> - Removed Tail -> Non-Tail fallback in the instruction selector. Since TF now should
>   handles all tail-call cases except where the return value type differs, this fallback
>   was not really useful and in fact caused unexpected behavior with variable
>   sized argument popping, since it wasn't possible to materialize a Return node
>   with the right pop count from the TailCall without additional context.
> - Modified existing Return generation to pass a constant zero as the additional
>   pop argument since the variable pop functionality
>
> LOG=N

TBR=bmeurer@chromium.org,mstarzinger@chromium.org,epertoso@chromium.org,danno@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
NOPRESUBMIT=true

Review-Url: https://codereview.chromium.org/2473643002
Cr-Commit-Position: refs/heads/master@{#40691}
2016-11-02 07:49:17 +00:00
bmeurer
5ef1bddf80 [compiler] Sanitize IC counts for vector based ICs.
All vector ICs use the TypeFeedbackVector::ComputeCounts method now,
while the remaining patching ICs still use the traditional way of
counting on the TypeFeedbackInfo hanging off the fullcodegen code
object. This fixes the problem that counts were sometimes off.

Drive-by-fix: Move FullCodeGenerator::CallIC to fullcodegen.cc.

R=yangguo@chromium.org

Review-Url: https://codereview.chromium.org/2472653002
Cr-Commit-Position: refs/heads/master@{#40690}
2016-11-02 06:01:09 +00:00
kozyatinskiy
3902043324 [inspector] migrate HeapProfiler to new style
BUG=none
R=dgozman@chromium.org

Review-Url: https://codereview.chromium.org/2474483003
Cr-Commit-Position: refs/heads/master@{#40689}
2016-11-02 00:52:31 +00:00
kozyatinskiy
8c08d423f3 [inspector] migrate Schema, Console, Profiler to new style
BUG=none
R=dgozman@chromium.org

Review-Url: https://codereview.chromium.org/2473563002
Cr-Commit-Position: refs/heads/master@{#40688}
2016-11-02 00:21:54 +00:00
kozyatinskiy
d5055bc932 Roll third_party/inspector_protocol to cf45a6e89b17cdc9eeacdef4c003fcc55f7ec2a0
This roll includes one change: "[inspector_protocol] support fall through and moveable Maybe" [1].

[1] https://codereview.chromium.org/2468923002/

BUG=none
R=dgozman@chromium.org

Review-Url: https://codereview.chromium.org/2469063002
Cr-Commit-Position: refs/heads/master@{#40687}
2016-11-01 22:33:39 +00:00
machenbach
b19abf5371 Revert "Create internal fields on global proxy objects"
This reverts commit 26547761ef.

Breaks layout tests:
https://build.chromium.org/p/client.v8.fyi/builders/V8-Blink%20Linux%2064/bui...

See also:
https://github.com/v8/v8/wiki/Blink-layout-tests

BUG=v8:5588
TBR=jochen@chromium.org, verwaest@chromium.org, hablich@chromium.org

Review-Url: https://codereview.chromium.org/2467073002
Cr-Commit-Position: refs/heads/master@{#40686}
2016-11-01 20:40:09 +00:00
ishell
a52ffd44fd [ic] Experiment: disable map-specific handler cache.
IC data handlers support most of the hot cases nowdays. Let's see if
the map-specific code cache still help us to improve things.

BUG=v8:5561

Review-Url: https://codereview.chromium.org/2462973003
Cr-Commit-Position: refs/heads/master@{#40685}
2016-11-01 11:18:36 +00:00
zhengxing.li
c1753f5c3d X87: [turbofan] Support variable size argument removal in TF-generated functions.
port 5319b50c85 (r40678)

  original commit message:
  This is preparation for using TF to create builtins that handle variable number of
  arguments and have to remove these arguments dynamically from the stack upon
  return.

  The gist of the changes:
  - Added a second argument to the Return node which specifies the number of stack
    slots to pop upon return in addition to those specified by the Linkage of the
    compiled function.
  - Removed Tail -> Non-Tail fallback in the instruction selector. Since TF now should
    handles all tail-call cases except where the return value type differs, this fallback
    was not really useful and in fact caused unexpected behavior with variable
    sized argument popping, since it wasn't possible to materialize a Return node
    with the right pop count from the TailCall without additional context.
  - Modified existing Return generation to pass a constant zero as the additional
    pop argument since the variable pop functionality

BUG=

Review-Url: https://codereview.chromium.org/2469623002
Cr-Commit-Position: refs/heads/master@{#40684}
2016-11-01 06:55:57 +00:00
adamk
a1381990a7 Remove --harmony-* flags for new Object static methods
Both --harmony-object-values-entries and --harmony-object-own-property-descriptors
are on by default in v8 5.4, which has now shipped to
stable as Chrome 54.

R=caitp@igalia.com

Review-Url: https://codereview.chromium.org/2464733003
Cr-Commit-Position: refs/heads/master@{#40683}
2016-10-31 22:53:35 +00:00
bjaideep
2c846a2ac7 PPC/s390: [turbofan] Support variable size argument removal in TF-generated functions
Port 5319b50c85

Original commit message:

    This is preparation for using TF to create builtins that handle variable number of
    arguments and have to remove these arguments dynamically from the stack upon
    return.

    The gist of the changes:
    - Added a second argument to the Return node which specifies the number of stack
      slots to pop upon return in addition to those specified by the Linkage of the
      compiled function.
    - Removed Tail -> Non-Tail fallback in the instruction selector. Since TF now should
      handles all tail-call cases except where the return value type differs, this fallback
      was not really useful and in fact caused unexpected behavior with variable
      sized argument popping, since it wasn't possible to materialize a Return node
      with the right pop count from the TailCall without additional context.
    - Modified existing Return generation to pass a constant zero as the additional
      pop argument since the variable pop functionality

R=danno@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2462173002
Cr-Commit-Position: refs/heads/master@{#40682}
2016-10-31 20:00:33 +00:00
lpy
9c78194343 [Tracing] Remove unused excluded categories list.
We only need included categories list, excluded categories list will only work
if we use regular expression in categories list, which is not supported in V8.

TBR=jochen@chromium.org

Review-Url: https://codereview.chromium.org/2462143002
Cr-Commit-Position: refs/heads/master@{#40681}
2016-10-31 19:45:20 +00:00
ahaas
da90034e02 [wasm] Do not run the infinite loop test if FLAG_dump_wasm_module is true
By not dumping the module of the test, we avoid adding code of an
infinite loop to the corpus of the wasm fuzzer.

R=bradnelson@chromium.org

NOTRY=true

Review-Url: https://codereview.chromium.org/2460313002
Cr-Commit-Position: refs/heads/master@{#40680}
2016-10-31 17:56:37 +00:00
ishell
597315dc13 [ic] Detailize some IC-specific runtime call stats counters.
This CL adds Load/StoreIC_Premonomorphic and detailizes IC_HandlerCacheHit bucket.

BUG=v8:5561

Review-Url: https://codereview.chromium.org/2459333003
Cr-Commit-Position: refs/heads/master@{#40679}
2016-10-31 17:48:34 +00:00
danno
5319b50c85 [turbofan] Support variable size argument removal in TF-generated functions
This is preparation for using TF to create builtins that handle variable number of
arguments and have to remove these arguments dynamically from the stack upon
return.

The gist of the changes:
- Added a second argument to the Return node which specifies the number of stack
  slots to pop upon return in addition to those specified by the Linkage of the
  compiled function.
- Removed Tail -> Non-Tail fallback in the instruction selector. Since TF now should
  handles all tail-call cases except where the return value type differs, this fallback
  was not really useful and in fact caused unexpected behavior with variable
  sized argument popping, since it wasn't possible to materialize a Return node
  with the right pop count from the TailCall without additional context.
- Modified existing Return generation to pass a constant zero as the additional
  pop argument since the variable pop functionality

LOG=N

Review-Url: https://codereview.chromium.org/2446543002
Cr-Commit-Position: refs/heads/master@{#40678}
2016-10-31 16:54:24 +00:00
jgravelle
fb96618ee0 Add Shell::PrintErr and expose it in the d8 shell as printErr
This function is implemented in other JavaScript shells

BUG=None

R=titzer

Review-Url: https://codereview.chromium.org/2458963003
Cr-Commit-Position: refs/heads/master@{#40677}
2016-10-31 16:40:33 +00:00
ishell
70d2b685ae [stubs] Fix allocation memento detection.
The old code does not work properly when the allocation memento object ends exactly at page boundary.

This CL addresses DBC mentioned in https://codereview.chromium.org/2313093002/

BUG=v8:5269

Review-Url: https://codereview.chromium.org/2466573002
Cr-Commit-Position: refs/heads/master@{#40676}
2016-10-31 15:51:03 +00:00
jbroman
fa33489ffd Remove DCHECK that transferred array buffers are neutered or shared.
While this seems like it should be true, the array buffer is not actually
neutered until the end of cloning. This is so that, if an exception is thrown
during serialization, the original array buffer is not left neutered. As a
result, Blink will not have neutered the buffer.

This fixes some DCHECK failures during layout tests.

BUG=chromium:148757

Review-Url: https://codereview.chromium.org/2466563002
Cr-Commit-Position: refs/heads/master@{#40675}
2016-10-31 15:23:30 +00:00
ishell
9dd638fe70 Minor fixes in objects printer.
BUG=

Review-Url: https://codereview.chromium.org/2468433002
Cr-Commit-Position: refs/heads/master@{#40674}
2016-10-31 15:16:51 +00:00
ishell
7c22a153e2 [ic] Simplify handling of primitive maps.
This CL adds support for primitive maps to
1) PrototypeIterator,
2) PropertyHandlerCompiler::CheckPrototypes(),
3) Map::GetOrCreatePrototypeChainValidityCell(),
4) Prototype checks in data-driven ICs.

BUG=v8:5561

Review-Url: https://codereview.chromium.org/2466553002
Cr-Commit-Position: refs/heads/master@{#40673}
2016-10-31 14:58:52 +00:00
jgruber
16310b2e39 [debugger] Ensure debug listeners do not throw
This exposes a couple of broken tests that used to silently throw within
the listener. Mark these as failing for now

BUG=v8:5330, v8:5581

Review-Url: https://codereview.chromium.org/2460833002
Cr-Commit-Position: refs/heads/master@{#40672}
2016-10-31 14:56:44 +00:00
vogelheim
36f3f90907 Speedup access to global_proxy.* attributes/accessors.
Using a global proxy (e.g. 'window.f', 'w.f' or 'this.f') is considerably slower than evaluating just 'f'. This CL aims to perform the necessary checks at compile time and inline the accesses.

This is a follow-on CL to crrev.com/2369933005:
- The initial upload is crrev.com/2369933005 + a rebase.
- The remaining issues are the fixes requested by the reviewers on that CL.

BUG=chromium:634276, chromium:654716, chromium:656959

Committed: https://crrev.com/8f43d748272536117008aa6a1b53ea52126261c1
Committed: https://crrev.com/041314524952a3c1bc71bd3beafbbb37319f1d22
Review-Url: https://codereview.chromium.org/2403003002
Cr-Original-Original-Commit-Position: refs/heads/master@{#40153}
Cr-Original-Commit-Position: refs/heads/master@{#40365}
Cr-Commit-Position: refs/heads/master@{#40671}
2016-10-31 14:28:27 +00:00
jochen
26547761ef Create internal fields on global proxy objects
BUG=v8:5588
R=verwaest@chromium.org

Review-Url: https://codereview.chromium.org/2467463002
Cr-Commit-Position: refs/heads/master@{#40670}
2016-10-31 14:16:24 +00:00
georgia.kouveli
70dfb5a0d6 [turbofan] Use an IntPtrConstant in WordEqual comparisons.
ZeroConstant is a NumberConstant, so does not get matched
in IntMatchers, which results in missing some opportunities
in instruction selection. Use IntPtrConstant instead, which
generates an Int32Constant or an Int64Constant depending on
the word size.

BUG=

Review-Url: https://codereview.chromium.org/2467473002
Cr-Commit-Position: refs/heads/master@{#40669}
2016-10-31 12:23:26 +00:00
neis
6442156635 [test] Skip the debug-liveedit-double-call mjsunit test.
It's marked as [PASS, FAIL] but keeps showing up as a test failure for me.

R=mstarzinger@chromium.org
BUG=v8:5587

Review-Url: https://codereview.chromium.org/2461343002
Cr-Commit-Position: refs/heads/master@{#40668}
2016-10-31 12:22:33 +00:00
ahaas
c4119758d8 [wasm] Use correct parameter type in wasm-run-utils.h
Due to a typo wasm-run-utils used the type of the first parameter for
all parameters. This caused problems if not all parameters had the same
type.

R=titzer@chromium.org, clemensh@chromium.org

Review-Url: https://codereview.chromium.org/2463743002
Cr-Commit-Position: refs/heads/master@{#40667}
2016-10-31 10:51:51 +00:00
cbruni
fde9039fed [stubs] Add FLAG_enable_slow_asserts check to CSA_SLOW_ASSERT
R=ishell@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2461463003
Cr-Commit-Position: refs/heads/master@{#40666}
2016-10-31 10:32:07 +00:00
bmeurer
639abf4fd4 [turbofan] Ship inlining into try blocks.
R=mstarzinger@chromium.org
BUG=v8:5267

Review-Url: https://codereview.chromium.org/2460333002
Cr-Commit-Position: refs/heads/master@{#40665}
2016-10-31 10:22:13 +00:00
epertoso
88366741fc [turbofan] Handle inlining of API getters/setters.
Similar to what crankshaft does, we introduce a mapcheck if necessary and a call to the CallApiCallbackStub.

BUG=

Review-Url: https://codereview.chromium.org/2458643002
Cr-Commit-Position: refs/heads/master@{#40664}
2016-10-31 10:10:25 +00:00
mstarzinger
b4b436de6a [compiler] Ship Ignition for all TurboFan code.
This enables Ignition unconditionally for all code that is destined for
optimization with TurboFan. This ensures all optimization attempts will
go through the BytecodeGraphBuilder and that the AstGraphBuilder pipe is
dried out in practice.

patch from issue 2427953002 at patchset 120001 (http://crrev.com/2427953002#ps120001)

R=mvstanton@chromium.org,rmcilroy@chromium.org

Review-Url: https://codereview.chromium.org/2453973004
Cr-Commit-Position: refs/heads/master@{#40663}
2016-10-31 09:43:43 +00:00