GitLab

Refactors the class PinchZoomViewport to (1) move it out of layer_tree_host_impl.* and (2) convert it to Chromium style.

BUG=none


Review URL: https://chromiumcodereview.appspot.com/11829006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@175996 0039d316-1c4b-4281-b951-d872f2087c98