cc: Simplify picture layer tiling update tile priorities.

This patch simplifies the priority math calculation and moves it
into layers space. This makes the priority to be less correct,
since we're inverse transforming the viewport into layer space
instead of forward transforming tiles into screen space in all cases.

In particular, with perspective and rotated layers, we will be marking
more tiles as visible than before. This should be OK, since the amount
of those layers in practice is limited.

BUG=339142

Review URL: https://codereview.chromium.org/140513006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251064 0039d316-1c4b-4281-b951-d872f2087c98
Android: add pliard@ to build/android/pylib/OWNERS

NOTRY=True

Review URL: https://codereview.chromium.org/163883002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251065 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251064
SVN changes up to revision 251065