I've already added some security checks to sanitize CompositorFrames wrt mus::Windows. A mus::Window can only refer to other mus::Window surfaces in its subtree. Thus, an arbitrary window cannot move a different arbitrary window. The window manager has the one true view of top level windows, and should not be moving them around using compositor frames, thus a malicious mus-gpu cannot move windows outside of the bounds of a top level window for the purposes of hit testing. Of course, mus-gpu can do other not so nice things, but that's no worse than the current gpu process I believe.

This bug refers to things that are no longer a problem but the fundamental issue still needs ot be resolved. Window Tree Updates should be pushed from Mus-gpu to Mus-ws. CompositorFrames no longer use type converters. This is very input related so I'm adding a few relevant folks.

Based on our latest discussions, I don't believe we want to pursue this architecture in the short term. Closing.