aura-mus: add a drag representation image.

services/ui/ws/window_tree.h

Index: services/ui/ws/window_tree.h
diff --git a/services/ui/ws/window_tree.h b/services/ui/ws/window_tree.h
index 4a03b181d9bd620f0c1650990eb315e56b9546f2..9bbeaafa5e3698b96b075e4c9b80ca610a4a5be2 100644
--- a/services/ui/ws/window_tree.h
+++ b/services/ui/ws/window_tree.h
@@ -17,6 +17,7 @@
 
 #include "base/callback.h"
 #include "base/macros.h"
+#include "base/memory/weak_ptr.h"
 #include "cc/ipc/surface_id.mojom.h"
 #include "mojo/public/cpp/bindings/associated_binding.h"
 #include "services/ui/public/interfaces/window_tree.mojom.h"
@@ -372,6 +373,11 @@ class WindowTree : public mojom::WindowTree,
   void NotifyChangeCompleted(uint32_t change_id,
                              mojom::WindowManagerErrorCode error_code);
 
+  // Callback for when WmMoveDragImage completes. This sends off the next
+  // queued move under the image if the mouse had further moves while we were
+  // waiting for the last move to be acknowledged.
+  void OnWmMoveDragImageCompleted();
+
   // WindowTree:
   void NewWindow(uint32_t change_id,
                  Id transport_window_id,
@@ -460,8 +466,12 @@ class WindowTree : public mojom::WindowTree,
   void PerformDragDrop(
       uint32_t change_id,
       Id source_window_id,
+      const gfx::Point& screen_location,
       const std::unordered_map<std::string, std::vector<uint8_t>>& drag_data,
-      uint32_t drag_operation) override;
+      const SkBitmap& drag_image,
+      const gfx::Vector2d& drag_image_offset,
+      uint32_t drag_operation,
+      ui::mojom::DragEventSource source) override;
   void CancelDragDrop(Id window_id) override;
   void PerformWindowMove(uint32_t change_id,
                          Id window_id,
@@ -500,6 +510,7 @@ class WindowTree : public mojom::WindowTree,
       const ServerWindow* window) const override;
 
   // DragSource:
+  void OnDragContinued(const gfx::Point& location) override;
   void OnDragCompleted(bool success, uint32_t action_taken) override;
   ServerWindow* GetWindowById(const WindowId& id) override;
   DragTargetConnection* GetDragTargetForWindow(
@@ -586,6 +597,19 @@ class WindowTree : public mojom::WindowTree,
       waiting_for_top_level_window_info_;
   bool embedder_intercepts_events_ = false;
 
+  // Whether we're waiting for an ack from a WmMoveDragImage message.

[sky, 2017/03/23 00:05:36]

Similar to WindowManager please put the state related to a drag into it's own
struct.

[Elliot Glaysher, 2017/03/23 19:58:44]

Done. But I left the weak_factory_ in WindowTree (and renamed) as I'm unsure if
its safe to have a factory to an object in another one. I can't think of a
reason this would be so, but...

+  bool waiting_for_move_drag_ack_ = false;
+
+  // Whether we've queued a move to |queued_cursor_location_| when we get an
+  // ack from WmMoveDragImage.
+  bool has_queued_drag_window_move_ = false;
+
+  // When |has_queued_drag_window_move_| is true, this is a location which
+  // should be sent to the window manager as soon as it acked the last one.
+  gfx::Point queued_cursor_location_;
+
+  base::WeakPtrFactory<WindowTree> weak_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(WindowTree);
 };