Version 4.4.63.17 (cherry-pick)

Merged b199bcdd

unicode-decoder: fix out-of-band write in utf16

BUG=v8:4274,chromium:508540
LOG=N
TBR=hablich@chromium.org

Review URL: https://codereview.chromium.org/1227203010 .

Cr-Commit-Position: refs/branch-heads/4.4@{#21}
Cr-Branched-From: 2e4c5505-refs/heads/4.4.63@{#1}
Cr-Branched-From: 0208b8e3-refs/heads/master@{#28333}