Many places in the JavaScript standard library are changed in ES2015 from
getting an integer using ToUint32 to using ToLength. This patch stages
the flag turning on those new semantics.

BUG=v8:3087,v8:4244
LOG=Y
R=adamk

Review URL: https://codereview.chromium.org/1426673003

Cr-Commit-Position: refs/heads/master@{#31641}