Update V8 to version 4.3.48.2 (cherry-pick).

Summary of changes available at:
https://chromium.googlesource.com/v8/v8/+log/eb476c80..bc4c36e6

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

TBR=yangguo@chromium.org

Review URL: https://codereview.chromium.org/1021243002

Cr-Commit-Position: refs/heads/master@{#321555}

DEPS

@@ -47,7 +47,7 @@ vars = {
   # the commit queue can handle CLs rolling Skia
   # and V8 without interference from each other.
   'v8_branch': 'trunk',
-  'v8_revision': 'eb476c8027c418c92aa0438be7e505d8ddd89444',
+  'v8_revision': 'bc4c36e63a8f0cee3398ec0b72da5bdfafba3954',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling WebRTC
   # and V8 without interference from each other.