DEPS.xwalk: Roll v8-crosswalk (262b54e -> c4640c3).

c4640c3 Merge pull request #32 from dp7/master
9f30235 Merge pull request #34 from fenghaitao/setTruncatingFlag
69be78f Set kTruncatingToInt32 flag if one of the SIMD operand requires Integer32
773c161 Merge pull request #33 from fenghaitao/master
ca3023f Fixed a typo: psrlq -> psrldq.
2a06d56 V8 profiling patch rebased on Chromium v36
6756718 Merge pull request #31 from huningxin/fix_int32x4_select
c537192 Merge pull request #30 from huningxin/fix_ia32_debug
2daf654 Fix SIMD.int32x4.select to return and accept input type as float32x4
03a03f2 Fix ia32 debug build issue.
a0f0edc Merge pull request #22 from rakuco/backport-urlretrieve-fix
c2d1700 Backport r21402 from the bleeding_edge branch.
Merge pull request #2035 from rakuco/v8-xwalk-roll

DEPS.xwalk: Roll v8-crosswalk (262b54e -> c4640c3).