gpu: FreeEverything in gles2 if we're not visible.

This patch ensures that FreeEverything again after a shallow flush
when visibility is false.

[email protected]
BUG=498995

Review URL: https://codereview.chromium.org/1179953007

Cr-Commit-Position: refs/heads/master@{#334303}
4 files changed