Animation support for rich notifications on Mac.

The following animations are added:
1) Sliding animation is played when a popup shows.
2) Fade-out animation is used when a popup closes.
3) Bounds animation is performed when popups get updated or repositioned.

The animations are serialized to avoid potential conflicts on the screen. For example, when a popup is being closed, we will first fade-out this popup. Then all the popups below are moved up with the animation. After that, the new popup could slide in.

BUG=238246
TEST=existing tests updated to work with animations
R=dewittj@chromium.org, rsesek@chromium.org

Review URL: https://codereview.chromium.org/15681005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@202163 0039d316-1c4b-4281-b951-d872f2087c98
6 files changed