[Do not revert] Roll-back V8 to version 4.4.63.

Update the V8 version to the one used for the upcoming Chromium branch M44.
If this CL results in failed tests please contact the test owners.
They most likely need to make changes to deal with the roll-back.

Original roll: https://crrev.com/1224d1ad48f94177798158fdc0e3e7faed8635ab

When in doubt please try to contact the committer.

TBR=machenbach@chromium.org,vogelheim@chromium.org,yangguo@chromium.org,danno@chromium.org

Review URL: https://codereview.chromium.org/1136893003

Cr-Commit-Position: refs/heads/master@{#329629}

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': '15c8b709750615005f4d2fec88e22bb4f4731614',
+  'v8_revision': '2e4c5505e85d94b520e853dda3f0cc3f2769e5f0',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling WebRTC
   # and V8 without interference from each other.