drawSystemFocusRing should take canvas transformations into account.

In addition, the accessible rect needs to be applied to ancesetor elements
within the canvas, otherwise their bounding boxes may be clipped.

BUG=261998

Review URL: https://chromiumcodereview.appspot.com/23314002

git-svn-id: svn://svn.chromium.org/blink/trunk@156371 bbb929c8-8fbe-4397-9dbb-9b2b20218538