Revert "Enable --harmony-function-tostring by default"

This reverts commit c3dda0bbac.

Reason for revert: Breaks gc stress bots:
https://build.chromium.org/p/client.v8/builders/V8%20Linux%20-%20gc%20stress/builds/14266

Original change's description:
> Enable --harmony-function-tostring by default
>
> Update tests to work with new behavior.
>
> This feature is shipping in Firefox 54, so compatibility risk is low.
>
> R=​littledan@chromium.org, adamk@chromium.org, caitp@igalia.com
> CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel
>
> Bug: v8:4958
> Cq-Include-Trybots: master.tryserver.v8:v8_linux_noi18n_rel_ng
> Change-Id: Ib16d19468cf935f961d7bcd856ebbeb5692d3e61
> Reviewed-on: https://chromium-review.googlesource.com/546941
> Commit-Queue: Josh Wolfe <jwolfe@igalia.com>
> Reviewed-by: Adam Klein <adamk@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#50178}

TBR=adamk@chromium.org,hablich@chromium.org,kozyatinskiy@chromium.org,littledan@chromium.org,caitp@igalia.com,jwolfe@igalia.com

Change-Id: Ie5dd0bd2b97ae6d0126edec6373e48abe0eeb3f0
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:4958
Reviewed-on: https://chromium-review.googlesource.com/832649
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50182}

src/flag-definitions.h

@@ -210,6 +210,7 @@ DEFINE_IMPLICATION(harmony_class_fields, harmony_public_fields)
 
 // Features that are complete (but still behind --harmony/es-staging flag).
 #define HARMONY_STAGED(V)                                               \
+  V(harmony_function_tostring, "harmony Function.prototype.toString")   \
   V(harmony_restrict_constructor_return,                                \
     "harmony disallow non undefined primitive return value from class " \
     "constructor")                                                      \
@@ -221,7 +222,6 @@ DEFINE_IMPLICATION(harmony_class_fields, harmony_public_fields)
   V(harmony_regexp_named_captures, "harmony regexp named captures")     \
   V(harmony_regexp_property, "harmony Unicode regexp property classes") \
   V(harmony_async_iteration, "harmony async iteration")                 \
-  V(harmony_function_tostring, "harmony Function.prototype.toString")   \
   V(harmony_promise_finally, "harmony Promise.prototype.finally")
 
 #ifdef V8_INTL_SUPPORT

test/message/fail/paren_in_arg_string.out

@@ -1,6 +1,6 @@
-undefined:1: SyntaxError: Arg string terminates parameters early
-(function anonymous()
-                    ^
-SyntaxError: Arg string terminates parameters early
+*%(basename)s:29: SyntaxError: Function arg string contains parenthesis
+var paren_in_arg_string_bad = new Function(')', 'return;');
+                              ^
+SyntaxError: Function arg string contains parenthesis
     at new Function (<anonymous>)
     at *%(basename)s:29:31

test/mjsunit/harmony/async-generators-basic.js

@@ -153,7 +153,7 @@ async function* asyncGeneratorForToString() {}
 assertEquals("async function* asyncGeneratorForToString() {}",
              asyncGeneratorForToString.toString());
 
-assertEquals("async function*() {}", async function*() {}.toString());
+assertEquals("async function* () {}", async function*() {}.toString());
 assertEquals("async function* namedAsyncGeneratorForToString() {}",
              async function* namedAsyncGeneratorForToString() {}.toString());
 
@@ -164,9 +164,9 @@ assertEquals("async *method() { }",
 assertEquals("async *method() { }",
              (new (class { async *method() { } })).method.toString());
 
-assertEquals("async function* anonymous(\n) {\n\n}",
+assertEquals("async function* anonymous() {\n\n}",
              AsyncGeneratorFunction().toString());
-assertEquals("async function* anonymous(\n) {\n\n}",
+assertEquals("async function* anonymous() {\n\n}",
              (new AsyncGeneratorFunction()).toString());
 
 // ----------------------------------------------------------------------------

test/mjsunit/regress/regress-2470.js

@@ -46,4 +46,4 @@ assertThrows('Function("a", "", "//", "//")', SyntaxError);
 // Some embedders rely on the string representation of the resulting
 // function in cases where no formal parameters are specified.
 var asString = Function("return 23").toString();
-assertSame("function anonymous(\n) {\nreturn 23\n}", asString);
+assertSame("function anonymous() {\nreturn 23\n}", asString);

test/mjsunit/regress/regress-crbug-109362.js

@@ -14,16 +14,15 @@ function test(expectation, f) {
 }
 
 /*
-(function(
-) {
+(function() {
 1 + reference_error //@ sourceURL=evaltest
 })
 */
-test("3:5", new Function(
+test("2:5", new Function(
     '1 + reference_error //@ sourceURL=evaltest'));
 /*
 (function(x
-) {
+/\**\/) {
 
  1 + reference_error //@ sourceURL=evaltest
 })
@@ -35,7 +34,7 @@ test("4:6", new Function(
 
 ,z//
 ,y
-) {
+/\**\/) {
 
  1 + reference_error //@ sourceURL=evaltest
 })
@@ -45,7 +44,7 @@ test("7:6", new Function(
 /*
 (function(x/\*,z//
 ,y*\/
-) {
+/\**\/) {
 1 + reference_error //@ sourceURL=evaltest
 })
 */

test/mjsunit/regress/regress-crbug-663410.js

@@ -4,5 +4,5 @@
 
 function alert(x) {};
 assertThrows(
-  'Function("a=`","`,xss=1){alert(xss)")'
+  Function("a=`","`,xss=1){alert(xss)")
 );

test/mozilla/mozilla.status

@@ -118,10 +118,6 @@
   # Invalid according to ES2015 syntax. (Details: crbug.com/726625)
   'ecma_3/extensions/regress-368516': [FAIL],
 
-  # Function.prototype.toString revision.
-  # (https://chromium-review.googlesource.com/c/546941#message-5dc0f5efe277388501e8870e39ec70383dfc7db8)
-  'js1_5/Scope/regress-185485': [FAIL],
-
   ##################### SKIPPED TESTS #####################
 
   # This test checks that we behave properly in an out-of-memory