Commit Graph

1718 Commits

Author SHA1 Message Date
jarin
4142bc6bc1 [turbofan] Restrict types in load elimination.
In simplified numbering, we make sanity checks based on types (e.g.,
NumberSubtract should take numbers as inputs), but this can be
violated if optimization passes make types less precise.

In this CL, we fix load elimination to make sure that types are
smaller in the store -> load elimination by taking an intersection
of the load's type with the store value's type and inserting a guard
with that type. Note that the load type comes from type feedback, so
it can be disjoint from the stored value type (in that case, this
must be dead code because the map chack for the load should prevent
us from using the stored value).

BUG=chromium:599412
LOG=n

Review URL: https://codereview.chromium.org/1857133003

Cr-Commit-Position: refs/heads/master@{#35259}
2016-04-05 12:30:14 +00:00
ishell
792bf2a093 [crankshaft] Fix environment handling after leaving inlined tail call.
BUG=chromium:537444, v8:4698
LOG=N
TBR=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/1859763005

Cr-Commit-Position: refs/heads/master@{#35253}
2016-04-05 09:43:56 +00:00
bmeurer
e5724d958b [frames] Also properly deal with TF builtins in OptimizedFrame::GetFunctions().
This was missing from the previous fix.

R=ishell@chromium.org
BUG=chromium:599714
LOG=n

Review URL: https://codereview.chromium.org/1861583002

Cr-Commit-Position: refs/heads/master@{#35249}
2016-04-05 06:41:20 +00:00
mstarzinger
6ab9c1850f Fix resuming generator marked for optimization.
This fixes a corner case where the generator function of a suspended
generator has been marked for optimization. We assume the optimization
approach will cause a bailout because generators are not optimized. But
resuming is more resilient by always activating the unoptimized code.

R=neis@chromium.org,bmeurer@chromium.org
TEST=mjsunit/regress/regress-crbug-513471
BUG=chromium:513471
LOG=n

Review URL: https://codereview.chromium.org/1856683002

Cr-Commit-Position: refs/heads/master@{#35234}
2016-04-04 11:52:09 +00:00
ishell
4598356f17 Properly complete in-object slack tracking.
BUG=chromium:599003
LOG=N

Review URL: https://codereview.chromium.org/1856653002

Cr-Commit-Position: refs/heads/master@{#35232}
2016-04-04 10:00:44 +00:00
ishell
c7ff5766cf Display a meaningfull error message when trying to capture a stack trace to a proxy.
... instead of RUNTIME_ASSERT pointing to V8 guts.

BUG=chromium:599067
LOG=N

Review URL: https://codereview.chromium.org/1844223004

Cr-Commit-Position: refs/heads/master@{#35227}
2016-04-04 08:37:30 +00:00
ishell
ecb8fcfcca [crankshaft] [turbofan] Fix environment handling when generating a tail call from inlined function.
This CL ensures that we build environments/frame states so that tail caller frame will never become topmost.

BUG=chromium:598998, v8:4698
LOG=N

Review URL: https://codereview.chromium.org/1849503002

Cr-Commit-Position: refs/heads/master@{#35188}
2016-04-01 07:22:47 +00:00
bmeurer
6df9a22c3f [ic] Use the CallFunction builtin to invoke accessors.
The HandlerCompiler did not properly handle the weird edge case when a
sloppy mode function was installed as an accessor on one of the value
wrapper prototypes and then accessed via a load from a primitive value.
In this case we just passed the primitive value untouched instead of
properly wrapping it first. The CallFunction builtin properly deals with
all the funny edge cases, so we use it instead of duplicating almost all
of the logic here (the performance difference is neglible).

R=verwaest@chromium.org
BUG=chromium:599073, v8:4413
LOG=n

Review URL: https://codereview.chromium.org/1845243005

Cr-Commit-Position: refs/heads/master@{#35187}
2016-04-01 06:37:57 +00:00
yangguo
297daf6c37 [debugger] allow debug-evaluate to change stack and context values.
R=bmeurer@chromium.org, cbruni@chromium.org, ulan@chromium.org
BUG=chromium:124206,chromium:569811
LOG=N

Review URL: https://codereview.chromium.org/1834633003

Cr-Commit-Position: refs/heads/master@{#35145}
2016-03-31 06:00:21 +00:00
bmeurer
978ad03b92 [crankshaft] Address the deoptimization loops of Math.floor, Math.round and Math.ceil.
Fix and re-enable the flexible representation for Math.floor (which is used to
implement Math.ceil) and Math.round, which allows Math.floor and Math.round to
return double results instead of int32, and therefore allows values outside
the int32 range, especially -0 is now a valid result, which doesn't deopt.

Also port this feature to x64 and ia32 when the CPU supports the SSE4.1
extension.

This addresses all the known deoptimization loops related to Math.round
in the Kraken benchmark suite, and seems to also address most of the
deoptimization loops related to Math.floor in the Oort Online benchmark.

Drive-by-fix: Import the regression tests for the broken HMathFloorOfDiv
optimization that caused the initial revert of the feature (for arm64 only
back then).

BUG=chromium:476477,v8:2890,v8:4059
R=jarin@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/1841513003

Cr-Commit-Position: refs/heads/master@{#35094}
2016-03-29 10:24:54 +00:00
adamk
06403470e3 Remove --harmony-regexps flag
It's been on since M49. Also moved tests from harmony -> es6,
one of which was merged with another test of the same name.

While moving stuff over to regexp.js, I also noticed that there
were unused calls to %FunctionSetName and %SetNativeFlag (those
calls are already handled by InstallGetter()).

Review URL: https://codereview.chromium.org/1838563003

Cr-Commit-Position: refs/heads/master@{#35076}
2016-03-25 23:02:11 +00:00
binji
88724ec4cb [Atomics] Fix atomic access index validation
BUG=v8:4737
LOG=n
R=jarin@chromium.org

Review URL: https://codereview.chromium.org/1676613002

Cr-Commit-Position: refs/heads/master@{#35074}
2016-03-25 21:52:52 +00:00
littledan
97fce6214e Check for proper types from error handling code
A bug in error printing meant that we failed to do proper type checks
before calling into C++ code, which could lead to RUNTIME_ASSERT
failures if methods are called on alternative receivers. This patch
adds the right type checks.

BUG=chromium:596718
LOG=Y
R=adamk

Review URL: https://codereview.chromium.org/1831053003

Cr-Commit-Position: refs/heads/master@{#35069}
2016-03-25 02:10:02 +00:00
adamk
ed18aa65ea Remove support for legacy const, part 1
Now that ES2015 const has shipped, in Chrome 49, legacy const declarations
are no more. This lets us remove a bunch of code from many parts of the
codebase.

In this patch, I remove parser support for generating legacy const variables
from const declarations. This also removes the special "illegal declaration"
bit from Scope, which has ripples into all compiler backends.

Also gone are any tests which relied on legacy const declarations.

Note that we do still generate a Variable in mode CONST_LEGACY in one case:
function name bindings in sloppy mode. The likely fix there is to add a new
Variable::Kind for this case and handle it appropriately for stores in each
backend, but I leave that for a later patch to make this one completely
subtractive.

Review URL: https://codereview.chromium.org/1819123002

Cr-Commit-Position: refs/heads/master@{#35002}
2016-03-22 17:52:13 +00:00
adamk
249bf75e0c Remove runtime flags for Proxy and Reflect
Both of them shipped in Chrome 49 without incident.

Also move relevant tests from harmony/ to es6/.

Review URL: https://codereview.chromium.org/1815773002

Cr-Commit-Position: refs/heads/master@{#34964}
2016-03-21 19:40:02 +00:00
ishell
e6dca379b6 [crankshaft] Check if the function is callable before generating a tail call via Call builtin.
This is necessary to ensure that "Called non callable" exception will get a proper message and stack trace even for calls at tail position.

BUG=chromium:595615, v8:4698
LOG=N

Review URL: https://codereview.chromium.org/1818003002

Cr-Commit-Position: refs/heads/master@{#34962}
2016-03-21 19:24:28 +00:00
bmeurer
cc04776632 [json] Allow any callable object for toJSON.
Previously only JSFunctions seemed to be valid for toJSON, which doesn't
match the ES6 specification that allows any object with [[Call]]
internal method (i.e. any Callable in V8 terminology), including bound
functions and proxies.

BUG=chromium:595738, chromium:535408
R=yangguo@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/1824533002

Cr-Commit-Position: refs/heads/master@{#34913}
2016-03-20 19:35:28 +00:00
adamk
6a8de15322 Several mjsunit cleanups
- Move default parameters tests from harmony/ to es6/ and remove
    non-existent --harmony-default-parameters flag.
  - Remove some non-existent tests from mjsunit.status

Review URL: https://codereview.chromium.org/1812313002

Cr-Commit-Position: refs/heads/master@{#34908}
2016-03-18 23:20:44 +00:00
yangguo
1e2d0e1136 [regexp] catch stack overflow when parsing back references.
R=jkummerow@chromium.org
BUG=chromium:595657
LOG=N

Review URL: https://codereview.chromium.org/1811913006

Cr-Commit-Position: refs/heads/master@{#34894}
2016-03-18 14:52:41 +00:00
verwaest
c6f9883d53 Remove oob elements collected from the prototype chain by trimming in GetArrayKeys
BUG=chromium:594953
LOG=n

Review URL: https://codereview.chromium.org/1817443003

Cr-Commit-Position: refs/heads/master@{#34893}
2016-03-18 14:37:36 +00:00
littledan
7acee1ef61 Throw the right exceptions from setting elements in Array.prototype.concat
This patch fixes two bugs in Array.prototype.concat in conjunction with
subclassing Arrays:
- Create a new property rather than calling Set when adding elements to
  the output array. This means setters are not called.
- If there is an exception thrown from DefineProperty, propagate it
  outwards properly, rather than swallowing it. This can occur, e.g., with
  a Proxy as the new output array.

R=adamk
LOG=Y
BUG=chromium:595319

Review URL: https://codereview.chromium.org/1814933002

Cr-Commit-Position: refs/heads/master@{#34876}
2016-03-17 22:42:00 +00:00
mvstanton
2aa070be4f InstanceOfStub incorrectly interprets the hole as a prototype.
Repair this to match what the runtime correctly does, by first checking if the
function is a constructor before we access the prototype.

R=verwaest@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1810953002

Cr-Commit-Position: refs/heads/master@{#34863}
2016-03-17 14:32:23 +00:00
jarin
c2e82d6e82 [crankshaft] Fix inlining to always connect both branches of test context.
BUG=v8:4839
LOG=n

Review URL: https://codereview.chromium.org/1811693002

Cr-Commit-Position: refs/heads/master@{#34848}
2016-03-17 10:00:21 +00:00
littledan
f9db79ebdb Ship ES2015 restrictions on function declaration locations
Function declarations were previously permitted by V8 in many locations
which no ECMAScript specification allowed; the ECMAScript 2015 spec
enumerates a few locations (in blocks, as well as after labels and in
conditionals when in sloppy mode). This patch ships the flag to restrict
the usage of function declarations to those contexts.

R=adamk
LOG=Y
BUG=v8:4824
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_chromium_rel_ng;tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1799233003

Cr-Commit-Position: refs/heads/master@{#34828}
2016-03-16 16:39:23 +00:00
jkummerow
84dd29bb3c Fix polymorphic keyed load handler selection for string elements
The monomorphic case already carefully ensures that we don't try to use
a regular elements load stub on string wrapper elements. The polymorphic
path must perform an equivalent check.

BUG=chromium:594955
LOG=n
R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/1806543002

Cr-Commit-Position: refs/heads/master@{#34807}
2016-03-16 10:56:16 +00:00
adamk
108efd7f54 Remove Scope::scope_contains_with_ bit
This part of Scope has existed since V8's initial check in, but from what
I can tell it's not required to implement "with". The only tests that
depend upon it are tests of the debugger and the Scope mirrors, but the
resulting test behavior after removing the bit still seems perfectly
reasonable to me. In fact, with the included fix for scope name collection,
the scope mirror is actually improved with this change.

As a bi-product, this fixes the attached bug, about the contains_with
bit having inconsistent values in some arrow function compilation
scenarios.

BUG=chromium:592353
LOG=n
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1804783002

Cr-Commit-Position: refs/heads/master@{#34802}
2016-03-15 22:41:59 +00:00
cbruni
96a2bd8ae8 [builtins] Fix Array.prototype.concat bug
Array.prototype.concat did not work correct with complex elements on the
receiver or the prototype chain.

BUG=chromium:594574
LOG=y

Review URL: https://codereview.chromium.org/1804963002

Cr-Commit-Position: refs/heads/master@{#34798}
2016-03-15 20:29:28 +00:00
caitpotter88
3088979d5c [runtime] fix getting element keys from SLOW_SLOPPY_ARGUMENTS_ELEMENTS
BUG=v8:4825
LOG=N
R=jkummerow@chromium.org, cbruni@chromium.org

Review URL: https://codereview.chromium.org/1778023004

Cr-Commit-Position: refs/heads/master@{#34754}
2016-03-14 17:10:50 +00:00
jarin
4d4bd54f0a [turbofan] Fix operand calculation for constant materialization from frame.
BUG=chromium:582702
LOG=N

Review URL: https://codereview.chromium.org/1781393002

Cr-Commit-Position: refs/heads/master@{#34736}
2016-03-13 20:21:41 +00:00
ishell
690c7a854a [turbofan] Avoid dereferencing empty handle when inlining a tail call.
BUG=chromium:593697,v8:4698
LOG=N

Review URL: https://codereview.chromium.org/1781303002

Cr-Commit-Position: refs/heads/master@{#34716}
2016-03-11 11:41:29 +00:00
adamk
dea9559457 Remove destructuring and default arguments runtime flags
These flags have been on by default since version 4.9, which has been
in stable Chrome for over a week now, demonstrating that they're
here to stay.

Also moved the tests out of harmony/ and into es6/.

Review URL: https://codereview.chromium.org/1776683003

Cr-Commit-Position: refs/heads/master@{#34692}
2016-03-10 23:22:30 +00:00
rossberg
4614c7caaf [strong] Remove all remainders of strong mode
R=mstarzinger@chromium.org,bmeurer@chromium.org,adamk@chromium.org
BUG=v8:3956
LOG=Y

Review URL: https://codereview.chromium.org/1773653002

Cr-Commit-Position: refs/heads/master@{#34669}
2016-03-10 12:45:42 +00:00
littledan
ca5deb1ff8 Ensure appropriate bounds checking for Array subclass concat
When an Array subclass is used as the receiver for concat, or with
certain usages of @@species, the output that's constructed is of
a different type with new slow path logic. This slow path still
made references to elements, so it's important that bounds checking
for a too-long result still be done. This patch repairs that bounds
checking.

R=cbruni
LOG=Y
BUG=chromium:592340

Review URL: https://codereview.chromium.org/1782443002

Cr-Commit-Position: refs/heads/master@{#34636}
2016-03-09 18:54:44 +00:00
jkummerow
32b3d3e931 [arm/arm64][stubs] Fix d16-d31 preservation on stub failure
Reading the registers' values back from the FrameDescription
should use the same offset computation as storing them into it.
The offsets must also match what the deoptimizer expects, which
is rx at offset rx.code() * kDoubleSize, even if some registers
are not saved (leaving gaps).

BUG=v8:4800
LOG=n
R=danno@chromium.org

Review URL: https://codereview.chromium.org/1769833006

Cr-Commit-Position: refs/heads/master@{#34633}
2016-03-09 17:36:07 +00:00
yangguo
d1f68f776e [regexp] fix bogus assertion in CharacterRange constructor.
The CharacterRange constructor checks the input for validity. However,
CharacterRange::Singleton also uses the constructor and may have
kEndMarker as input, causing the check to fail.

The solution is to move the check to CharacterRange::Range and
consistently use it across the code base.

R=jkummerow@chromium.org
BUG=chromium:593282
LOG=N

Review URL: https://codereview.chromium.org/1776013003

Cr-Commit-Position: refs/heads/master@{#34626}
2016-03-09 15:55:38 +00:00
jarin
69c84fe460 [turbofan] Fix deoptimization stack layout for fast literal comparisons.
BUG=chromium:592341
LOG=n

Review URL: https://codereview.chromium.org/1776013002

Cr-Commit-Position: refs/heads/master@{#34615}
2016-03-09 12:36:09 +00:00
jarin
9867a8a26e [turbofan] Fix register constraint for memory barrier.
After fixing the memory barrier for maps (https://codereview.chromium.org/1714513003), we are using a temp register for the map case. The temp register should not be aliased with the stored value (otherwise we perform the mem barrier check with a wrong value). This CL makes sure it is not aliased.

BUG=chromium:590074
LOG=n

Review URL: https://codereview.chromium.org/1775083002

Cr-Commit-Position: refs/heads/master@{#34607}
2016-03-09 09:39:51 +00:00
titzer
5c1c98e829 [wasm] Rename _WASMEXP_ object to Wasm.
R=ahaas@chromium.org,binji@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1770383002

Cr-Commit-Position: refs/heads/master@{#34587}
2016-03-08 14:48:27 +00:00
mstarzinger
2669224274 [compiler] Remove support for concurrent OSR.
R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/1773593002

Cr-Commit-Position: refs/heads/master@{#34572}
2016-03-08 09:02:44 +00:00
yangguo
9113402b53 [debugger] break at each initialization in a multiple var declaration.
R=rossberg@chromium.org
BUG=v8:4807
LOG=N

Committed: https://crrev.com/ee98147ea0d994bcfb0d14d43f490ee828d2426f
Cr-Commit-Position: refs/heads/master@{#34531}

Review URL: https://codereview.chromium.org/1768973002

Cr-Commit-Position: refs/heads/master@{#34540}
2016-03-07 13:41:18 +00:00
machenbach
c6dbb071a3 Revert of [debugger] break at each initialization in a multiple var declaration. (patchset #1 id:1 of https://codereview.chromium.org/1768973002/ )
Reason for revert:
[Sheriff] Breaks layout tests:
https://build.chromium.org/p/client.v8.fyi/builders/V8-Blink%20Linux%2064/builds/5160

Original issue's description:
> [debugger] break at each initialization in a multiple var declaration.
>
> R=rossberg@chromium.org
> BUG=v8:4807
> LOG=N
>
> Committed: https://crrev.com/ee98147ea0d994bcfb0d14d43f490ee828d2426f
> Cr-Commit-Position: refs/heads/master@{#34531}

TBR=rossberg@chromium.org,yangguo@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:4807

Review URL: https://codereview.chromium.org/1770783003

Cr-Commit-Position: refs/heads/master@{#34538}
2016-03-07 12:53:55 +00:00
yangguo
ee98147ea0 [debugger] break at each initialization in a multiple var declaration.
R=rossberg@chromium.org
BUG=v8:4807
LOG=N

Review URL: https://codereview.chromium.org/1768973002

Cr-Commit-Position: refs/heads/master@{#34531}
2016-03-07 12:00:16 +00:00
yangguo
f9d7c711af [regexp] Fix off-by-one in CharacterRange::Negate.
Character ranges starting at 1 are not correctly negated.

R=jkummerow@chromium.org
BUG=chromium:592343
LOG=Y

Review URL: https://codereview.chromium.org/1768093002

Cr-Commit-Position: refs/heads/master@{#34528}
2016-03-07 11:00:01 +00:00
bmeurer
0c35579093 [crankshaft] Fix invalid ToNumber optimization.
We cannot optimize away ToNumber conversions based on the Type that we
see in Crankshaft, as this might be the (unchecked or even pretruncated)
lower bound. We can only use the HType, which is based on the definition.

R=jkummerow@chromium.org
BUG=chromium:590989
LOG=n

Review URL: https://codereview.chromium.org/1757013002

Cr-Commit-Position: refs/heads/master@{#34445}
2016-03-02 19:28:04 +00:00
yangguo
d9fe836dd4 [debugger] fix break locations for assignments and return.
We used to emit debug break location on block entry. This cannot be
ported to the interpreted as we do not emit bytecode for block entry.
This made no sense to begin with though, but accidentally added
break locations for var declarations.

With this change, the debugger no longer breaks at var declarations
without initialization. This is in accordance with the fact that the
interpreter does not emit bytecode for uninitialized var declarations.

Also fix the bytecode to match full-codegen's behavior wrt return
positions:
- there is a break location before the return statement, with the source
  position of the return statement.
- right before the actual return, there is another break location. The
  source position points to the end of the function.

R=rmcilroy@chromium.org, vogelheim@chromium.org
TBR=rossberg@chromium.org
BUG=v8:4690
LOG=N

Review URL: https://codereview.chromium.org/1744123003

Cr-Commit-Position: refs/heads/master@{#34388}
2016-03-01 12:47:55 +00:00
neis
0ad44590e0 [json] Fix iteration over object keys in InternalizeJSONProperty.
We must not use for-of since that could be observed.

R=yangguo@chromium.org
BUG=v8:4769
LOG=n

Review URL: https://codereview.chromium.org/1748633002

Cr-Commit-Position: refs/heads/master@{#34387}
2016-03-01 11:53:28 +00:00
bmeurer
d00da47b61 [turbofan] Don't use the CompareIC in JSGenericLowering.
The CompareICStub produces an untagged raw word value, which has to be
translated to true or false manually in the TurboFan code. But for lazy
bailout after the CompareIC, we immediately go back to fullcodegen or
Ignition with the raw value, to a location where both fullcodegen and
Ignition expect a boolean value, which might crash or in the worst case
(depending on the exact computation inside the CompareIC) could lead to
arbitrary memory access.

Short-term fix is to use the proper runtime functions (unified with the
interpreter now) for comparisons. Next task is to provide optimized
versions of these based on the CodeStubAssembler, which can then be used
via code stubs in TurboFan or directly in handlers in the interpreter.

R=mstarzinger@chromium.org
BUG=v8:4788
LOG=n

Review URL: https://codereview.chromium.org/1738153002

Cr-Commit-Position: refs/heads/master@{#34335}
2016-02-26 18:41:35 +00:00
bmeurer
58ab990aa8 [turbofan] Bailout if LoadBuffer typing assumption doesn't hold.
The LoadBuffer operator that is used for asm.js heap access claims to
return only the appropriate typed array type, but out of bounds access
could make it return undefined. So far we tried to "repair" the graph
later if we see that our assumption was wrong, and for various reasons
that worked for some time. But now that wrong type information that is
propagated earlier is picked up appropriately and thus we generate wrong
code, i.e. we in the repro case we feed NaN into ChangeFloat64Uint32 and
thus get 2147483648 instead of 0 (with proper JS truncation).

This was always considered a temporary hack until we have a proper
asm.js pipeline, but since we still run asm.js through the generic
JavaScript pipeline, we have to address this now. Quickfix is to just
bailout from the pipeline when we see that the LoadBuffer type was
wrong, i.e. the result of LoadBuffer is not properly truncated and thus
undefined or NaN would be observable.

R=mstarzinger@chromium.org, jarin@chromium.org
BUG=chromium:589792
LOG=y

Review URL: https://codereview.chromium.org/1740123002

Cr-Commit-Position: refs/heads/master@{#34322}
2016-02-26 11:06:30 +00:00
mstarzinger
3baa290264 [fullcodegen] Fix assert for operand stack depth tracking.
This fixes a corner case that triggered an assert in full-codegens
operand stack depth tracking. We stop pushing operands if we overflow
the C-stack while iterating the AST. This makes the tracking go out of
sync before we fully returned from the tree traversal, at which point
the thrown RangeError will abort compilation.

R=ishell@chromium.org
TEST=mjsunit/regress/regress-crbug-589472
BUG=chromium:589472
LOG=n

Review URL: https://codereview.chromium.org/1732903002

Cr-Commit-Position: refs/heads/master@{#34255}
2016-02-24 16:29:47 +00:00
bmeurer
6cc5c601b6 [crankshaft] Fix deopt loop in String.fromCharCode on non-int32 inputs.
The Crankshaft fast case for String.fromCharCode() unconditionally
deoptimizes on all non-int32 inputs, even tho it would be perfectly
valid to just truncate the index to an int32.

R=ishell@chromium.org
BUG=chromium:587068
LOG=n

Review URL: https://codereview.chromium.org/1727873003

Cr-Commit-Position: refs/heads/master@{#34243}
2016-02-24 10:59:55 +00:00