Address TODOs in the new layer painting and hit testing.

Address TODOs in the new layer painting and hit testing.

-ASSERT(layer()->parent()) in all the transform codepaths since
the RenderView cannot have a transform.
-Early return if the content rect does not intersect the
damage rect in the painting code. We don't need to do
any of the filter and/or transparency dance if we're
not going to paint anything. This also allowed for
removing the shouldPaintContent bool.
-Remove a random style() null check that can't be hit.

R=abarth@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/c27c5e71f7b47b1c797107dc4e04e0b9dca033d5

[abarth-chromium, 2015-02-21 02:10:37]

abarth@chromium.org changed reviewers:
+ abarth@chromium.org

[abarth-chromium, 2015-02-21 02:10:38]

lgtm

[ojan, 2015-02-21 02:19:33]

Committed patchset #2 (id:20001) manually as
c27c5e71f7b47b1c797107dc4e04e0b9dca033d5 (presubmit successful).