cc: Rename PictureLayerTiling(Set) Iterator to CoverageIterator

Both of the PLT and PLTSet iterators are specific to geometry coverage
of some rect.  Calling them CoverageIterator makes this more clear.

R=danakj@chromium.org
BUG=none


Review URL: https://chromiumcodereview.appspot.com/12583018

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@191218 0039d316-1c4b-4281-b951-d872f2087c98
8 files changed