Get rid of LayerFragment.

Get rid of LayerFragment.

We don't have fragmentation. So no need for this abstraction.
This simplifies a lot of code so that we can do less work.
For example, we can check shouldPaintContent only up in
paintLayerContents instead of in each nested function.

Instead of passing the LayerFragment, pass the layer location
and the clip rect for each nested function.

R=esprehn@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/9c0e21b11665b34ec12af0572e25438e70c9da11

[esprehn, 2014-12-09 01:35:01]

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

[esprehn, 2014-12-09 01:35:01]

lgtm

[ojan, 2014-12-09 01:37:48]

Committed patchset #2 (id:20001) manually as
9c0e21b11665b34ec12af0572e25438e70c9da11.