Move hit testing out of RenderLayer into RenderBox.

Move hit testing out of RenderLayer into RenderBox.

Change hit testing to walk over the render tree instead of
the RenderLayer tree. This is a step in the direction of
removing the RenderLayer tree entirely.

For now, there's a few calls back into RenderLayer that
will be removed in a followup patch. This patch also
breaks hit testing on transformed inlines. I'll be
removing the ability to transform inlines in a
followup patch anyways, so it's ok for hit testing
to give the wrong result temporarily here.

Almost all of this patch is just moving code from
RenderLayer to RenderBox. The primary substantive change
is in RenderBox::hitTestLayer. Instead of having
hitTestChildren calls, we call collectSelfPaintingLayers,
reverse sort by z-index (so we start at the top),
and then iterate over the result.

The test-case also exposes that we don't correctly hit
transformed elements inside inline-blocks. I went back as
far as 4153b8a515d54275934d4244aaf2d5a7a8fe3333 and the
bug still happened.

R=abarth@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/47eb802054ee5f6999af66f845dd068f96c8f7f8

[abarth-chromium, 2015-02-20 05:18:23]

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

[abarth-chromium, 2015-02-20 05:18:23]

lgtm

[ojan, 2015-02-20 05:31:47]

Committed patchset #3 (id:40001) manually as
47eb802054ee5f6999af66f845dd068f96c8f7f8 (presubmit successful).