Refactor CCLayerTreeHostCommon -  merge visible rect computation into calc draw transforms.

To aid the design of intelligent prepainting, and to clean up the code anyway, it's appropriate to do this.
Unit tests are already in place that cover this refactoring.

BUG=154442
R=enne@chromium.org

Review URL: https://chromiumcodereview.appspot.com/11079012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@160676 0039d316-1c4b-4281-b951-d872f2087c98
8 files changed