Revert of [Android] Stop hiding the RWHV layer subtree when hiding the widget

Revert of [Android] Stop hiding the RWHV layer subtree when hiding the widget (patchset #10 id:270001 of https://codereview.chromium.org/1001573003/)

Reason for revert:
Breaks Android WebView which does not call ApplicationStatus.initialize

Original issue's description:
> [Android] Preserve the front buffer when the activity is paused
>
> Currently, when an activity is stopped, we explicitly hide the
> foreground Tab. This is problematic, as current hiding semantics
> might clear the visual front buffer before the window is hidden.
> This in turn causes an unpleasant flickering during activity
> transitions, e.g., when backgrounding Chrome or locking the screen.
>
> Wire Activity onPause/onResume notifications to WindowAndroidObservers,
> allowing the foreground tab to preserve its front buffer while hiding
> its web content. If the tab is explicitly hidden, or the root window
> is lost, the front buffer will be cleared as usual.
>
> BUG=462752, 434401
>
> Committed: https://crrev.com/764f31d287a4995f0c89915745f5749e1c7063af
> Cr-Commit-Position: refs/heads/master@{#322052}

TBR=sievers@chromium.org,dtrainor@chromium.org,tedchoc@chromium.org,piman@chromium.org,torne@chromium.org,jdduke@chromium.org
BUG=462752, 434401
Committed: https://crrev.com/8f4d93f89393359f6a6f73ad06a0619027a0ca95
Cr-Commit-Position: refs/heads/master@{#322170}

[boliu, 2015-03-25 14:41:14]

Created Revert of [Android] Stop hiding the RWHV layer subtree when hiding the
widget

[boliu, 2015-03-25 14:41:34]

The CQ bit was checked by boliu@chromium.org

[commit-bot: I haz the power, 2015-03-25 14:42:02]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1038573004/1

[commit-bot: I haz the power, 2015-03-25 16:19:14]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-25 16:19:48]

Patchset 1 (id:??) landed as
https://crrev.com/8f4d93f89393359f6a6f73ad06a0619027a0ca95
Cr-Commit-Position: refs/heads/master@{#322170}