cc: Fix HeadsUpDisplayLayerImpl NPE after resource loss

Currently will NPE in HeadsUpDisplayLayerImpl::UpdateHudTexture
immediately after a DidLoseOutputSurface call that throws away the
resource. Resource loss can happen quite frequently under normal usage
in Android WebView.

Also fixed a condition WillDraw as writing the test for issue above.

Fix for internal bug b/11164012.

TEST=HeadsUpDisplayLayerImplTest.UpdateAfterResourceLoss
BUG=

Review URL: https://codereview.chromium.org/26277008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228222 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228222