Fix LayoutTest animations/fill-mode-reverse.html

This was testing forwards fill incorrectly. The Web Animations implementation
is correct, the legacy implementation is not.

Also, the behavior it tests is mostly covered by
animations/animation-direction-reverse-fill-mode.html, so it should be merged
with that test.

R=dstockwell

Review URL: https://codereview.chromium.org/36543002

git-svn-id: svn://svn.chromium.org/blink/trunk@160322 bbb929c8-8fbe-4397-9dbb-9b2b20218538
More informative error messages for non-Transferables.

Elaborate the TypeError exception reported if the various
postMessage()s (on window, at the dedicated Worker global scope, or
over MessagePorts) are ill-typed transferable arguments, supplying an
error message indicating that the transferable argument isn't a
sequence type.

R=
BUG=308730

Review URL: https://codereview.chromium.org/30673002

git-svn-id: svn://svn.chromium.org/blink/trunk@160323 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove failing expectation for virtual/web-animations-css/animations/3d/state-at-end-event-transform.html

This test has been passing reliably for some time.

R=dstockwell

Review URL: https://codereview.chromium.org/36463003

git-svn-id: svn://svn.chromium.org/blink/trunk@160324 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Updating test expectations

git-svn-id: svn://svn.chromium.org/blink/trunk@160325 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add self to watchlist for <track>

BUG=none

Review URL: https://codereview.chromium.org/36673002

git-svn-id: svn://svn.chromium.org/blink/trunk@160326 bbb929c8-8fbe-4397-9dbb-9b2b20218538