context.addHitRegion() is not working when using transform operation.

Should be able to add hit region when using transform operation.
context.isClipMode uses SkClipStack::getSaveCount() internally.
But the count is incremented by transform operation as well as clip operation.
So, remove the method and then add a new method which is determined by only clip operation.

BUG=389862

Review URL: https://codereview.chromium.org/352793006

git-svn-id: svn://svn.chromium.org/blink/trunk@177483 bbb929c8-8fbe-4397-9dbb-9b2b20218538