[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