mash: Preliminary support for widget hit test masks

components/mus/public/interfaces/window_tree.mojom

Index: components/mus/public/interfaces/window_tree.mojom
diff --git a/components/mus/public/interfaces/window_tree.mojom b/components/mus/public/interfaces/window_tree.mojom
index e5a15f16c23aee0782e43a591ccf288a242eacd7..c73f49a07252c9af062a5aebfc7c421986387e50 100644
--- a/components/mus/public/interfaces/window_tree.mojom
+++ b/components/mus/public/interfaces/window_tree.mojom
@@ -129,6 +129,11 @@ interface WindowTree {
                 mojo.Insets insets,
                 array<mojo.Rect>? additional_client_areas);
 
+  // Mouse events outside a hit test mask do not hit the window. The |mask| is
+  // in window local coordinates.
+  // TODO(jamescook): Convert |mask| to a path. http://crbug.com/613210
+  SetHitTestMask(uint32 window_id, mojo.Rect mask);

[sky, 2016/05/19 18:13:17]

Add support for a null mask that clears the hit test mask.

[James Cook, 2016/05/19 21:47:45]

Done.

+
   // Sets the visibility of the specified window to |visible|. Connections are
   // allowed to change the visibility of any window they have created, as well
   // as any of their roots.