Removing GL context rate limiting feature and related wrappers

Dead code removal.

BUG=531659
TBR=jamesr@chromium.org, vmiura@chromium.org
NOPRESUBMIT=true

Review URL: https://codereview.chromium.org/1341423006

Cr-Commit-Position: refs/heads/master@{#350172}
36 files changed