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 a1e8152c6986e628d6156a051f13157c0647e596..37a80c2b08fe07a5875872cbf501264f0da88c32 100644
--- a/components/mus/public/interfaces/window_tree.mojom
+++ b/components/mus/public/interfaces/window_tree.mojom
@@ -106,6 +106,12 @@ interface WindowTree {
   // can delete it.
   DeleteWindow(uint32 change_id, uint32 window_id);
 
+  // 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);
 
@@ -267,6 +273,9 @@ interface WindowTreeClient {
   // previously embedded in. See Embed() for more information.
   OnUnembed(uint32 window);
 
+  // Sent when a window loses capture.
+  OnLostCapture(uint32 window);
+
   // Called in response to NewTopLevelWindow() successfully completing.
   OnTopLevelCreated(uint32 change_id, WindowData data);