Fix toolbar drawing problem when clearing the clip rect.

Fix toolbar drawing problem when clearing the clip rect.

To repro this, it required changing the source code to force
the bad state, but the result is very consistent with bugs
we have received on this.

The changes made were:
1.) Exit the overview mode in Activity#onStart
2.) Change LayoutManagerChrome#hideOverview(false)

  Old code:
  startHiding(Tab.INVALID_TAB_ID, false);
  doneHiding();

  New code:
  activeLayout.onTabSelecting(time(), Tab.INVALID_TAB_ID);
  activeLayout.forceAnimationToFinish();

At this point, go to the tab switcher and hit the recents
button twice.  Chrome should have exited the tab switcher and
every few times the toolbar would either be half clipped or
fully clipped.

Added logs and it only would be broken if we ever set a clip
rect (sometimes it was skipped entirely as the animations start
and finish pre-empted it).

BUG=515522
Review URL: https://codereview.chromium.org/1408773003

Cr-Commit-Position: refs/heads/master@{#354948}

Committed: https://chromium.googlesource.com/chromium/src/+/82895c55b876484395c3967d8d827d0b1133f94e

[Ted C, 2015-10-27 23:34:52]

Committed patchset #1 (id:1) manually as
82895c55b876484395c3967d8d827d0b1133f94e.