[Canvas toDataURL] Disable JPEG subsampling at maximum quality

When a JPEG toDataURL is created and maximum quality (1.0) is requested,
disable JPEG subsampling.

New layout test: fast/canvas/canvas-toDataURL-jpeg-maximum-quality.html

BUG=251500

Review URL: https://codereview.chromium.org/82813002

git-svn-id: svn://svn.chromium.org/blink/trunk@162676 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add missing initialization of spellCheckerClient in PageClients

It was missed in r162114.

Review URL: https://codereview.chromium.org/85623008

git-svn-id: svn://svn.chromium.org/blink/trunk@162677 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Web Animations CSS: Avoid waiting for cancelled compositor animation

When a renderer associated with a composited animation is destroyed, other
animations waiting for a synchronized start may never be notified. We can
detect this case and start such animations immediately. After this change
CSSPendingAnimations now requests service on every frame until all pending
animations have a chance to start.

BUG=322272

Review URL: https://codereview.chromium.org/83793017

git-svn-id: svn://svn.chromium.org/blink/trunk@162678 bbb929c8-8fbe-4397-9dbb-9b2b20218538