Use correct creation context during Iterable.forEach iteration

Use |thisValue| instead of |scriptState->context()->Global()|, since this
is simpler and since Global() actually returns a WindowProxy object that
may change and become incorrect to use as creation context depending on
what the callback function does.


Review URL:

Cr-Commit-Position: refs/heads/master@{#389785}
(cherry picked from commit 0cd7a9f853e3cb7c035b4ab9e07a503552267f9d)

Review URL: .

Cr-Commit-Position: refs/branch-heads/2661@{#671}
Cr-Branched-From: ef6f6ae5e4c96622286b563658d5cd62a6cf1197-refs/heads/master@{#378081}
2 files changed