Update V8 to version 4.3.56.

Update V8 to version 4.3.56.

Summary of changes available at:
https://chromium.googlesource.com/v8/v8/+log/c5443d75..b09c6a7d

Please follow these instructions for assigning/CC'ing issues:
https://code.google.com/p/v8-wiki/wiki/TriagingIssues

TBR=hablich@chromium.org,machenbach@chromium.org,yangguo@chromium.org,vogelheim@chromium.org
BUG=

Committed: https://crrev.com/16408c2845040574d5e458703f848aa04b2bb629
Cr-Commit-Position: refs/heads/master@{#322237}

[Michael Achenbach, 2015-03-25 18:59:21]

The CQ bit was checked by machenbach@chromium.org

[commit-bot: I haz the power, 2015-03-25 18:59:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1005693012/1

[commit-bot: I haz the power, 2015-03-25 21:24:14]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-25 21:26:31]

Patchset 1 (id:??) landed as
https://crrev.com/16408c2845040574d5e458703f848aa04b2bb629
Cr-Commit-Position: refs/heads/master@{#322237}

[loislo, 2015-03-26 10:11:47]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/997883003/ by loislo@chromium.org.

The reason for reverting is: number of crashes in DevTools layout tests


3605	  if (p->owner()->identity() != CODE_SPACE) return false;
(gdb) bt
#0  IsOnInvalidatedCodeObject (addr=<optimized out>) at
../../v8/src/heap/mark-compact.cc:3605
#1  v8::internal::SlotsBuffer::UpdateSlotsWithFilter (this=0x51d8988d820,
heap=0x51d892af040) at ../../v8/src/heap/mark-compact.cc:4725
#2  0x0000000001bf4a3f in UpdateSlotsRecordedIn (heap=0x51d892af040,
buffer=<optimized out>, code_slots_filtering_required=<optimized out>) at
../../v8/src/heap/mark-compact.h:330
#3  v8::internal::MarkCompactCollector::EvacuateNewSpaceAndCandidates
(this=0x51d892b4fc8) at ../../v8/src/heap/mark-compact.cc:3761
#4  0x0000000001be8838 in v8::internal::MarkCompactCollector::SweepSpaces
(this=0x51d892b4fc8) at ../../v8/src/heap/mark-compact.cc:4448
#5  0x0000000001be745f in v8::internal::MarkCompactCollector::CollectGarbage
(this=0x51d892b4fc8) at ../../v8/src/heap/mark-compact.cc:377
#6  0x0000000001bb662b in v8::internal::Heap::MarkCompact (this=0x51d892af040)
at ../../v8/src/heap/heap.cc:1274
#7  0x0000000001bb4d31 in v8::internal::Heap::PerformGarbageCollection
(this=0x51d892af040, collector=v8::internal::MARK_COMPACTOR,
gc_callback_flags=v8::kNoGCCallbackFlags) at ../../v8/src/heap/heap.cc:1159
#8  0x0000000001bb46b2 in v8::internal::Heap::CollectGarbage
(this=0x51d892af040, collector=<optimized out>, gc_reason=<optimized out>,
collector_reason=<optimized out>, gc_callback_flags=<optimized out>)
    at ../../v8/src/heap/heap.cc:894
#9  0x0000000001bb3a46 in CollectGarbage (space=v8::internal::OLD_POINTER_SPACE,
gc_reason=0x0, callbackFlags=v8::kNoGCCallbackFlags, this=<optimized out>) at
../../v8/src/heap/heap-inl.h:567
#10 CollectAllGarbage (this=0x51d892af040, flags=0,
gc_callback_flags=v8::kNoGCCallbackFlags, gc_reason=<optimized out>) at
../../v8/src/heap/heap.cc:784
#11 v8::internal::Heap::HandleGCRequest (this=0x51d892af040) at
../../v8/src/heap/heap.cc:735
#12 0x0000000001b5804b in v8::internal::StackGuard::HandleInterrupts
(this=0x51d892b54c8) at ../../v8/src/execution.cc:663
#13 0x0000000001fff9ac in __RT_impl_Runtime_StackGuard (isolate=<optimized out>,
args=...) at ../../v8/src/runtime/runtime-internal.cc:119
#14 v8::internal::Runtime_StackGuard (args_length=<optimized out>,
args_object=0x1139a18f7c28, isolate=<optimized out>) at
../../v8/src/runtime/runtime-internal.cc:109



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