cc: Make UpdateTilePriorities a separate step

This will make it more obvious in traces where work is really being done
and make it possible to optimize this further.

Comparing average times spent in the renderer compositor while scrolling
Wikipedia's List of Pokemon page on an N4 in two different runs:

    Before change:
        UpdateDrawProperties: 0.754ms

    After change:
        UpdateDrawProperties: 0.249ms
        UpdateTilePriorities: 0.553ms

R=danakj@chromium.org
BUG=308244

Review URL: https://codereview.chromium.org/26880009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229590 0039d316-1c4b-4281-b951-d872f2087c98
Disable InvalidateInflightAlbumsIndexerTest on Mac

BUG=309160
TBR=tommycli@chromium.org

Review URL: https://codereview.chromium.org/29833003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229591 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229591