Remove computePaintInvalidationRectsIncludingNonCompositingDescendants

The function was used by the compositor code only so inlined it here.

Also fixed some issues with the function:
- it wasn't clearing the paint invalidation bits thus generating extra
unneeded invalidations. The fix is to make it generate the invaliation
as part of the paint invalidation phase by marking the renderer for full
invalidation.
- Removed tree walks as part of updating the previous paint invalidation
rectangle. We only really needed to clear it so that we don't invalidate
at the wrong position, the updating will be taken care of in a more
optimized way during the paint invalidation phase.

Review URL: https://codereview.chromium.org/580223002

git-svn-id: svn://svn.chromium.org/blink/trunk@182277 bbb929c8-8fbe-4397-9dbb-9b2b20218538