Add versions of isPointInPath, isPointInStroke that take a Path parameter.

Intent to implement:
  https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/MGxEfzBPw68

The spec reference is:
  http://www.w3.org/html/wg/drafts/2dcontext/master/#dom-context-2d-ispointinstroke
  http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#dom-context-2d-ispointinstroke

BUG=330506

Review URL: https://codereview.chromium.org/179383002

git-svn-id: svn://svn.chromium.org/blink/trunk@168437 bbb929c8-8fbe-4397-9dbb-9b2b20218538