Cherry-pick: aw: Release hardware onTrimMemory(MODERATE)

Clean cherry-pick of chromium r284591

BUG: 16412391

Original description:

Frameworks destroys the underlying EGLContext on after
certain levels of onTrimMemory, so webview must also release
its hardware draw resources to avoid using stale references.

Factor out release hardware resource code in
and, and call it in onTrimMemory.

Change-Id: I1945acc30d1a79c07a30ee9df136e6677b113d89
6 files changed