Reland: mus: Enable system modal windows

components/mus/ws/event_dispatcher.h

Index: components/mus/ws/event_dispatcher.h
diff --git a/components/mus/ws/event_dispatcher.h b/components/mus/ws/event_dispatcher.h
index 19b39b2bc314d2a98e5316d461a87350ac4be930..d9e41ae4d4c8ff5431988e250eb338ff231dd0eb 100644
--- a/components/mus/ws/event_dispatcher.h
+++ b/components/mus/ws/event_dispatcher.h
@@ -13,6 +13,7 @@
 #include "base/macros.h"
 #include "cc/surfaces/surface_id.h"
 #include "components/mus/public/interfaces/event_matcher.mojom.h"
+#include "components/mus/ws/modal_window_controller.h"
 #include "components/mus/ws/server_window_observer.h"
 #include "ui/gfx/geometry/rect_f.h"
 
@@ -60,6 +61,20 @@ class EventDispatcher : public ServerWindowObserver {
   // (indicated by returning |false|).
   bool SetCaptureWindow(ServerWindow* capture_window, bool in_nonclient_area);
 
+  // Adds a system modal window. The window remains modal to system until it is
+  // destroyed. There can exist multiple system modal windows, in which case the
+  // one that is visible and added most recently or shown most recently would be
+  // the active one.
+  void AddSystemModalWindow(ServerWindow* 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();
+
   // Retrieves the ServerWindow of the last mouse move.
   ServerWindow* mouse_cursor_source_window() const {
     return mouse_cursor_source_window_;
@@ -148,9 +163,11 @@ class EventDispatcher : public ServerWindowObserver {
   // way we continue to eat events until the up/cancel is received.
   void CancelPointerEventsToTarget(ServerWindow* window);
 
-  // Returns true if we're currently an observer for |window|. We are an
-  // observer for a window if any pointer events are targeting it.
-  bool IsObservingWindow(ServerWindow* window);
+  // Used to observe a window. Can be called multiple times on a window. To
+  // unobserve a window, UnobserveWindow() should be called the same number of
+  // times.
+  void ObserveWindow(ServerWindow* winodw);
+  void UnobserveWindow(ServerWindow* winodw);
 
   // Returns an Accelerator bound to the specified code/flags, and of the
   // matching |phase|. Otherwise returns null.
@@ -166,9 +183,12 @@ class EventDispatcher : public ServerWindowObserver {
 
   EventDispatcherDelegate* delegate_;
   ServerWindow* root_;
-  ServerWindow* capture_window_;
 
+  ServerWindow* capture_window_;
   bool capture_window_in_nonclient_area_;
+
+  ModalWindowController modal_window_controller_;
+
   bool mouse_button_down_;
   ServerWindow* mouse_cursor_source_window_;
 
@@ -188,6 +208,9 @@ class EventDispatcher : public ServerWindowObserver {
   // cancel or up.
   PointerIdToTargetMap pointer_targets_;
 
+  // Keeps track of number of observe requests for each observed window.
+  std::map<const ServerWindow*, uint8_t> observed_windows_;
+
   DISALLOW_COPY_AND_ASSIGN(EventDispatcher);
 };