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 1dd204e4af3d775a7e1c1949fd2a80d410df972c..7b6992d4a77353f41884cd1c52887da8abd8688f 100644
--- a/components/mus/public/interfaces/window_tree.mojom
+++ b/components/mus/public/interfaces/window_tree.mojom
@@ -104,6 +104,16 @@ interface WindowTree {
   // can delete it.
   DeleteWindow(uint32 change_id, uint32 window_id);
 
+  // Requests input event capture for the given |window_id|. When a window gains
+  // capture, current input events are canceled. The given window will receive
+  // all subsequent input until an alternate window is set via SetCapture, or
+  // ReleaseCapture is called for |window_id|. OnLostCapture is called to notify
+  // of capture ending.
+  SetCapture(uint32 change_id, uint32 window_id);

[sky, 2016/01/29 20:47:00]

Document capture is only allowed if the window is processing an event.

[jonross, 2016/02/01 18:52:22]

Done.

+
+  // 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);
 
@@ -264,6 +274,9 @@ 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);