aw: Ensure invalidation when pipeline is stalled

aw: Ensure invalidation when pipeline is stalled

* If CommitFrame is skipped to to stall, ensure we invalidate.
* Make sure force_invalidate does not get cancelled by a
  pending fallback tick.
* Allow hardware initialization even when visible rect is
  empty, so fallback tick is always in the right mode.
* Fix visible rect empty checks.

BUG=425372
Review URL: https://codereview.chromium.org/654403006

TBR=boliu@chromium.org
Cr-Commit-Position: refs/heads/master@{#300566}
(cherry picked from commit 6b96a049428fceb4af34a5ea92b106ae208ea75b)

Conflicts:
	android_webview/browser/browser_view_renderer.h
	android_webview/native/aw_contents.h

Committed: https://chromium.googlesource.com/chromium/src/+/edd88dfbf6331fab8cae4151a5f62455f551d2e8

[boliu, 2014-10-22 17:05:39]

Committed patchset #1 (id:1) manually as
edd88dfbf6331fab8cae4151a5f62455f551d2e8 (presubmit successful).