mus: Implement Window Server Capture

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 903c70e4a9fe3c72c586f31fdf4be9af907bff71..13c6e5746b86744a009151affad6e5639e9f421e 100644
--- a/components/mus/public/interfaces/window_tree.mojom
+++ b/components/mus/public/interfaces/window_tree.mojom
@@ -96,6 +96,12 @@ interface WindowTree {
   // can delete it.
   DeleteWindow(uint32 window_id) => (bool success);
 
+  // Requests input event capture for the given |window_id|.
+  SetCapture(uint32 change_id, uint32 window_id);
+
+  // Releases input event capture for the given |window_id|.
+  ReleaseCapture(uint32 change_id, uint32 window_id);
+
   // Sets the specified bounds of the specified window.
   SetWindowBounds(uint32 change_id, uint32 window_id, mojo.Rect bounds);
 
@@ -254,6 +260,9 @@ interface WindowTreeClient {
   // previously embedded in. See Embed() for more information.
   OnUnembed();
 
+  // Sent when a window loses capture.
+  OnLostCapture(uint32 window);
+
   // Invoked when a window's bounds have changed.
   OnWindowBoundsChanged(uint32 window,
                         mojo.Rect old_bounds,