mus: Implement interwindow drag and drop

ui/views/mus/native_widget_mus.h

Index: ui/views/mus/native_widget_mus.h
diff --git a/ui/views/mus/native_widget_mus.h b/ui/views/mus/native_widget_mus.h
index 4f47a751aa6d783dfea8ba8b87825e1aded5a96d..c7fcf7d5bf0056fcca48492b789cdd59ef91bd24 100644
--- a/ui/views/mus/native_widget_mus.h
+++ b/ui/views/mus/native_widget_mus.h
@@ -22,6 +22,7 @@
 #include "ui/views/mus/mus_export.h"
 #include "ui/views/mus/window_tree_host_mus.h"
 #include "ui/views/widget/native_widget_private.h"
+#include "ui/wm/public/drag_drop_delegate.h"
 
 namespace aura {
 namespace client {
@@ -51,6 +52,8 @@ class FocusController;
 }
 
 namespace views {
+class DropHelper;
+class DropTargetMus;
 class WidgetDelegate;
 
 // An implementation of NativeWidget that binds to a ui::Window. Because Aura
@@ -63,6 +66,7 @@ class VIEWS_MUS_EXPORT NativeWidgetMus
     : public internal::NativeWidgetPrivate,
       public aura::WindowDelegate,
       public aura::WindowTreeHostObserver,
+      public aura::client::DragDropDelegate,
       public NON_EXPORTED_BASE(ui::InputEventHandler) {
  public:
   NativeWidgetMus(internal::NativeWidgetDelegate* delegate,
@@ -164,7 +168,7 @@ class VIEWS_MUS_EXPORT NativeWidgetMus
   void RunShellDrag(View* view,
                     const ui::OSExchangeData& data,
                     const gfx::Point& location,
-                    int operation,
+                    int drag_operations,
                     ui::DragDropTypes::DragEventSource source) override;
   void SchedulePaintInRect(const gfx::Rect& rect) override;
   void SetCursor(gfx::NativeCursor cursor) override;
@@ -219,6 +223,12 @@ class VIEWS_MUS_EXPORT NativeWidgetMus
                    const gfx::Point& new_origin) override;
   void OnHostCloseRequested(const aura::WindowTreeHost* host) override;
 
+  // Overridden from aura::client::DragDropDelegate:
+  void OnDragEntered(const ui::DropTargetEvent& event) override;
+  int OnDragUpdated(const ui::DropTargetEvent& event) override;
+  void OnDragExited() override;
+  int OnPerformDrop(const ui::DropTargetEvent& event) override;
+
   // Overridden from ui::InputEventHandler:
   void OnWindowInputEvent(
       ui::Window* view,
@@ -272,6 +282,9 @@ class VIEWS_MUS_EXPORT NativeWidgetMus
   // and this is used to unsafely pass void* pointers around chrome.
   std::map<std::string, void*> native_window_properties_;
 
+  // Receives drop events for |window_|.
+  std::unique_ptr<DropTargetMus> drop_target_;
+
   // Aura configuration.
   std::unique_ptr<WindowTreeHostMus> window_tree_host_;
   aura::Window* content_;
@@ -281,6 +294,9 @@ class VIEWS_MUS_EXPORT NativeWidgetMus
   std::unique_ptr<aura::client::ScreenPositionClient> screen_position_client_;
   std::unique_ptr<wm::CursorManager> cursor_manager_;
 
+  std::unique_ptr<DropHelper> drop_helper_;
+  int last_drop_operation_;
+
   base::WeakPtrFactory<NativeWidgetMus> close_widget_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeWidgetMus);