Remove support for control tints.

This also allows us to remove the paintingDisabled() concept on GraphicsContext, since control tint update was implemented by "painting"
without a canvas, which means walking the render tree to invalidate paint
for controls affected by tint.

BUG=344109

Review URL: https://codereview.chromium.org/444233003

git-svn-id: svn://svn.chromium.org/blink/trunk@179781 bbb929c8-8fbe-4397-9dbb-9b2b20218538