Make TRANSPARENT windows be layered windows on win aura

This builds on jbauman's patch to plumb use_software_compositor
from here: https://codereview.chromium.org/23621054/

The motivation here is that we currently have very different
event, focus, activation paths on DWM vs. classic because of the
differences between when we use top-level windows and when we
don't. With this change, all translucent (i.e. shaped) windows
are converted to being top level (always), and are rendered by
the software compositor and are converted to layered windows for
rendering.

BUG=293218 and many other focus/activation bugs

Review URL: https://codereview.chromium.org/26888006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230981 0039d316-1c4b-4281-b951-d872f2087c98
Reach mojo::system::CoreImpl::Init() on Android

This CL adds enough machinery on Android so that we can initialize mojo_system.
There's still more work to do to actually load and execute the sample program.

R=darin@chromium.org,aa@chromium.org

Review URL: https://codereview.chromium.org/42613002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230982 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230981
SVN changes up to revision 230982