mus: Server-side implementation of modal windows

components/mus/ws/window_manager_state.h

Index: components/mus/ws/window_manager_state.h
diff --git a/components/mus/ws/window_manager_state.h b/components/mus/ws/window_manager_state.h
index af6f3899817b62427d9a4cddebf8c31c7b4c463e..b93cbfdcc6b3b4aa76ae305b978ac0373e10a3c4 100644
--- a/components/mus/ws/window_manager_state.h
+++ b/components/mus/ws/window_manager_state.h
@@ -66,12 +66,20 @@ class WindowManagerState : public EventDispatcherDelegate {
     return got_frame_decoration_values_;
   }
 
-  void SetCapture(ServerWindow* window, bool in_nonclient_area);
+  bool SetCapture(ServerWindow* window, bool in_nonclient_area);
   ServerWindow* capture_window() { return event_dispatcher_.capture_window(); }
   const ServerWindow* capture_window() const {
     return event_dispatcher_.capture_window();
   }
 
+  // Checks if |modal_window| is a visible modal window that blocks current
+  // capture window and if that's the case, releases the capture.
+  void ReleaseCaptureBlockedByModalWindow(const ServerWindow* modal_window);
+
+  // Checks if the current capture window is blocked by any visible modal window
+  // and if that's the case, releases the capture.
+  void ReleaseCaptureBlockedByAnyModalWindow();
+
   // Returns true if this is the WindowManager of the active user.
   bool IsActive() const;