Don't show video fullscreen until DidEnterFullscreen() is called

Don't show video fullscreen until DidEnterFullscreen() is called

For fullscreen video on android, We call showFullscreenOverlay() too early.
We should wait until DidEnterFullscreen() gets called, and then we should let the video element to request the surface view.
Otherwise, if enterFullscreenForElement fails, we will incorrectly showing the fullscreen video in the background.
This CL also removes the hideFullscreenOverlay() call since this is no longer needed.
When exiting fullscreen, video view will automatically be destroyed.

BUG=367346
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=173917

[qinmin, 2014-05-09 01:49:23]

PTAL

[aelias_OOO_until_Jul13, 2014-05-09 03:07:45]

lgtm.  I don't understand this very well but but trchen tells me it's legit.

[qinmin, 2014-05-12 21:12:53]

The CQ bit was checked by qinmin@chromium.org

[commit-bot: I haz the power, 2014-05-12 21:13:21]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/qinmin@chromium.org/277823002/20001

[commit-bot: I haz the power, 2014-05-12 22:25:28]

FYI, CQ is re-trying this CL (attempt #1).
Please consider checking whether the failures are real,
and report flakes to chrome-troopers@google.com.
The failing builders are:
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/6981)

[commit-bot: I haz the power, 2014-05-12 23:00:47]

Change committed as 173917

[qinmin, 2014-05-13 17:45:42]

A revert of this CL has been created in
https://codereview.chromium.org/284913002/ by qinmin@chromium.org.

The reason for reverting is: this breaks webview. DidEnterFullscreen will never
be received since webview doesn't support fullscreen api. As a result, video
won't enter fullscreen..