Record the reference time when Performance is constructed.

BUG=264490

Review URL: https://chromiumcodereview.appspot.com/23367007

git-svn-id: svn://svn.chromium.org/blink/trunk@156613 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add animated WebP image that uses 'no blend' option to Layout tests

This is to test the case when an animation frame is supposed to
overwrite the previous frame (instead of blending with previous frame).

This was added to libwebp in Chromium here:
https://codereview.chromium.org/22802020/

Also, this patch is in preparation for the Blink patch:
https://codereview.chromium.org/23068027/, where the
corresponding unit tests are also added.

BUG=
R=noel@chromium.org

Review URL: https://codereview.chromium.org/23129024

git-svn-id: svn://svn.chromium.org/blink/trunk@156614 bbb929c8-8fbe-4397-9dbb-9b2b20218538
MergeIdenticalElementsCommand should lazy attach.

Review URL: https://chromiumcodereview.appspot.com/22986029

git-svn-id: svn://svn.chromium.org/blink/trunk@156615 bbb929c8-8fbe-4397-9dbb-9b2b20218538