Revert "android: Add CHECK() calls to better understand memory corruption."

This reverts r237591. The added CHECK() breaks the Android WebView and
was added to help diagnose a now-fixed bug that turned out to be
unrelated.

BUG=332079
NOTRY=true

Review URL: https://codereview.chromium.org/106433010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243367 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243367
Moves management of transients out of Window

And into TransientWindowManager. Additionally moves handling of NULL
layer stacking into TransientStackingWindowClient. The tests that were
exercising these code paths have all been moved to ui/views/corewm.

Also wires up TransientStackingWindowClient in a couple of places that
didn't have it.

The order of removing from transient parent as well as destroying of
transient children is slightly differently than before. To get the
order exactly as it was would require some new specific observer
functions. I'm hoping we don't need those. Hopefully this doesn't
cause issues, if it does I'll revisit.

I ended up exposing convenience functions. That's because typing
something like:

views::corewm::TransientWindowManager::Get(window)->AddTransientChild()

was too much for me. There is also some subtlety in so far as the
Get() function that takes a const Window* may return NULL, where as
non-const never returns NULL.

Lastly I had to make Window friend TransientWindowManager. This is
temporary until I create a specific TransientWindowManagerObserver
that contains the two transient related observer functions in
WindowObserver.

BUG=none
TEST=none
R=ben@chromium.org

Review URL: https://codereview.chromium.org/115453004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243368 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243368