When native app window visibility changes due to either show/hide or minimize/un-minimize, the RWH will now be notified so that page visibility events fire in the renderer.

BUG=157300
TEST=Install window-state-sample (https://chrome.google.com/webstore/detail/window-state-sample/gjijpbgljcllmmhmbcdcaegdandpgpml). Hiding or minimizing the window will cause document.webkitHidden to be true. This can be observed by looking at its checkbox under the "last 10 seconds" readout area after restoring visibility.

Review URL: https://codereview.chromium.org/23473005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227677 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227677