[ObjC ARC] Converts ios/chrome/test/earl_grey:test_support to ARC.

Automatically generated ARCMigrate commit
Notable issues:
Added __unsafe_unretained annotation to ExecuteJavascript function in order to handle not-yet-ARC files.
BUG=624363
TEST=None

Review-Url: https://codereview.chromium.org/2684023003
Cr-Commit-Position: refs/heads/master@{#449278}
10 files changed