mash: Use the new mus drag and drop API to get drag working in mash.

ui/views/mus/drag_drop_client_mus.h

Index: ui/views/mus/drag_drop_client_mus.h
diff --git a/ui/views/mus/drag_drop_client_mus.h b/ui/views/mus/drag_drop_client_mus.h
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index 0000000000000000000000000000000000000000..bb0b2954591060644a19cae104f848190d168879
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+++ b/ui/views/mus/drag_drop_client_mus.h
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+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef UI_VIEWS_MUS_DRAG_DROP_CLIENT_MUS_H_
+#define UI_VIEWS_MUS_DRAG_DROP_CLIENT_MUS_H_
+
+#include "base/callback.h"
+#include "ui/base/dragdrop/drag_drop_types.h"
+#include "ui/wm/public/drag_drop_client.h"
+
+namespace aura {
+class Window;
+}
+
+namespace ui {
+class LocatedEvent;
+class OSExchangeData;
+class Window;
+}
+
+namespace views {
+
+// An aura client object that translates aura dragging methods to their
+// remote ui::Window equivalents.
+class DragDropClientMus : public aura::client::DragDropClient {
+ public:
+  DragDropClientMus(ui::Window* ui_window);
+  ~DragDropClientMus() override;
+
+  // Overridden from aura::client::DragDropClient:
+  int StartDragAndDrop(const ui::OSExchangeData& data,
+                       aura::Window* root_window,
+                       aura::Window* source_window,
+                       const gfx::Point& screen_location,
+                       int drag_operations,
+                       ui::DragDropTypes::DragEventSource source) override;
+  void DragUpdate(aura::Window* target, const ui::LocatedEvent& event) override;
+  void Drop(aura::Window* target, const ui::LocatedEvent& event) override;
+  void DragCancel() override;
+  bool IsDragDropInProgress() override;
+
+ private:
+  // Callback for StartDragAndDrop().
+  void OnMoveLoopEnd(bool* out_success,
+                     uint32_t* out_action,
+                     bool in_success,
+                     uint32_t in_action);
+
+  ui::Window* ui_window_;
+
+  base::Closure runloop_quit_closure_;
+
+  DISALLOW_COPY_AND_ASSIGN(DragDropClientMus);
+};
+
+}  // namespace views
+
+#endif  // UI_VIEWS_MUS_DRAG_DROP_CLIENT_MUS_H_