Convert hash maps in RuleSet from StringImpl* as key to AtomicString.

BUG=

Review URL: https://codereview.chromium.org/143483004

git-svn-id: svn://svn.chromium.org/blink/trunk@166747 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove initialized tracking code in WebGL classes

No longer needed as we always initialize vram in command buffer in gpu process

This is my per cleanup CL per week.

BUG=
TEST=tree
R=bajones@chromium.org,kbr@chromium.org

Review URL: https://codereview.chromium.org/158033002

git-svn-id: svn://svn.chromium.org/blink/trunk@166748 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Fixed a performance regression with the upload-canvas-2d-to-texture test

Overhead of creating new extension helper objects on the fly was far
more than I had originally anticipated.

TBR=kbr@chromium.org
BUG=341814

Review URL: https://codereview.chromium.org/138383008

git-svn-id: svn://svn.chromium.org/blink/trunk@166749 bbb929c8-8fbe-4397-9dbb-9b2b20218538