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This provides an implementation of the mojo surfaces service and a
sample with two mojo applications composing each other via surfaces. The
viewport / display hookup is a bit of a hack in this patch as is the
complete lack of scheduling logic, but it's enough to get started.

Review URL: https://codereview.chromium.org/361123002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@282856 0039d316-1c4b-4281-b951-d872f2087c98