Fix crash in WebContentsViewAura::WindowObserver that happens when switching tabs. The exact repro steps were:

1) open an empty page
2) print preview
3) open a new tab
4) go back to original tab
5) close print preview
6) switch to the new tab

The crash happened at step 4 because the second tab got removed from the same root window as the print preview's observer. We weren't unobserving all the children of the root window at that point.

BUG=318791
R=ben@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=235267

Review URL: https://codereview.chromium.org/69813005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235302 0039d316-1c4b-4281-b951-d872f2087c98
Disable NotificationsApiTest.TestPartialUpdate to unblock CQ.

BUG=319689
TEST=none
R=jianli@chromium.org
TBR=jianli@chromium.org

Review URL: https://codereview.chromium.org/68203026

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235303 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235302
Fix metro-ash tests. delegate_ in this derived class was shadowing the member in the base.

TBR=sky@chromium.org
BUG=

Review URL: https://codereview.chromium.org/73793002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235304 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235304