Remove incremental draw optimization from SkDebugCanvas

Remove incremental draw optimization from SkDebugCanvas

The SkDebugCanvas can be (or is currently) being used to draw to multiple
different canvases. If this use-case is intended, then storing draw
-related state in the canvas causes bugs.

Remove incremental draw from SkDebugCanvas. It can only optimize the
case where draw command index is advanced, no other changes are done
and no visualization is used. This case is not that critical, as it
happens only once per new frame at most. It causes bugs, because
one SkDebugCanvas is used to draw to multiple canvases.

Leave the draw to canvas in same state as it was passed in.

This fixes the debugger bugs where:
 * Old, stale image would stay on the raster canvas when a new image is
 loaded. Also happened with resizes.

 * Proper image for overdraw filter would be visible only for the first
   frame

Review URL: https://codereview.chromium.org/844493003