cc: Reset tiling size upon destruction.

Since bundles are shared, if at any point a tiling is deleted, we
have to make sure we clear the tiles on the current tree for that
tiling.

If we don't, we can run into a situation where a tiling is
deleted (and still exists on the twin at the same scale), then when
we sync we create a new tiling with bundles coming from the twin.
However, since the new tiling bounds are initially empty, we try
to create all the tiles in the interest rect. Since the tiling already
existed on the twin, it might already have the tiles on the current
tree.

BUG=328044
R=enne

Review URL: https://codereview.chromium.org/103693007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240744 0039d316-1c4b-4281-b951-d872f2087c98
Fix broken DCHECKs caused by associating data types in parallel (94093006).
DTCs can be stopped when in MODEL_LOADED state now.

BUG=325794

Review URL: https://codereview.chromium.org/109653006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240745 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240745