aw: Skip hardware onDraw when visible rect is empty

Framework does not clamp onDraw to only the visible area. However must
still request functor in this case to support rt-side animation, and to
obtain the correct draw matrix. This means HardwareRenderer must be able
to handle not having a parent frame available.

BUG=412623

Review URL: https://codereview.chromium.org/551023002

Cr-Commit-Position: refs/heads/master@{#294093}
2 files changed