Refactors RootViewDropTarget into a platform independent part,

DropHelper, and the platform specific part DropTarget. I've also moved
ownership/creation of the DropTarget to Widget. This makes it alot
easier for the windows side, in which DropTarget must implement
IDataObject.

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/165155

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@23020 0039d316-1c4b-4281-b951-d872f2087c98

14 files changed, 382 insertions, 239 deletions

diff --git a/views/widget/drop_helper.cc b/views/widget/drop_helper.cc
new file mode 100644
index 0000000..35dcbd0
--- /dev/null
+++ b/views/widget/drop_helper.cc
@@ -0,0 +1,135 @@
+// Copyright (c) 2006-2008 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.
+
+#include "views/widget/drop_helper.h"
+
+#include "app/drag_drop_types.h"
+#include "views/view.h"
+#include "views/widget/root_view.h"
+
+namespace views {
+
+DropHelper::DropHelper(RootView* root_view)
+    : root_view_(root_view),
+      target_view_(NULL),
+      deepest_view_(NULL) {
+}
+
+DropHelper::~DropHelper() {
+}
+
+void DropHelper::ResetTargetViewIfEquals(View* view) {
+  if (target_view_ == view)
+    target_view_ = NULL;
+  if (deepest_view_ == view)
+    deepest_view_ = NULL;
+}
+
+int DropHelper::OnDragOver(const OSExchangeData& data,
+                           const gfx::Point& root_view_location,
+                           int drag_operation) {
+  View* view = CalculateTargetViewImpl(root_view_location, data, true,
+                                       &deepest_view_);
+
+  if (view != target_view_) {
+    // Target changed notify old drag exited, then new drag entered.
+    NotifyDragExit();
+    target_view_ = view;
+    NotifyDragEntered(data, root_view_location, drag_operation);
+  }
+
+  return NotifyDragOver(data, root_view_location, drag_operation);
+}
+
+void DropHelper::OnDragExit() {
+  NotifyDragExit();
+  deepest_view_ = target_view_ = NULL;
+}
+
+int DropHelper::OnDrop(const OSExchangeData& data,
+                       const gfx::Point& root_view_location,
+                       int drag_operation) {
+  View* drop_view = target_view_;
+  deepest_view_ = target_view_ = NULL;
+  if (!drop_view)
+    return DragDropTypes::DRAG_NONE;
+
+  if (drag_operation == DragDropTypes::DRAG_NONE) {
+    drop_view->OnDragExited();
+    return DragDropTypes::DRAG_NONE;
+  }
+
+  gfx::Point view_location(root_view_location);
+  View::ConvertPointToView(NULL, drop_view, &view_location);
+  DropTargetEvent drop_event(data, view_location.x(), view_location.y(),
+                             drag_operation);
+  return drop_view->OnPerformDrop(drop_event);
+}
+
+View* DropHelper::CalculateTargetView(
+    const gfx::Point& root_view_location,
+    const OSExchangeData& data,
+    bool check_can_drop) {
+  return CalculateTargetViewImpl(root_view_location, data, check_can_drop,
+                                 NULL);
+}
+
+View* DropHelper::CalculateTargetViewImpl(
+    const gfx::Point& root_view_location,
+    const OSExchangeData& data,
+    bool check_can_drop,
+    View** deepest_view) {
+  View* view = root_view_->GetViewForPoint(root_view_location);
+  if (view == deepest_view_) {
+    // The view the mouse is over hasn't changed; reuse the target.
+    return target_view_;
+  }
+  if (deepest_view)
+    *deepest_view = view;
+  // View under mouse changed, which means a new view may want the drop.
+  // Walk the tree, stopping at target_view_ as we know it'll accept the
+  // drop.
+  while (view && view != target_view_ &&
+         (!view->IsEnabled() || !view->CanDrop(data))) {
+    view = view->GetParent();
+  }
+  return view;
+}
+
+void DropHelper::NotifyDragEntered(const OSExchangeData& data,
+                                   const gfx::Point& root_view_location,
+                                   int drag_operation) {
+  if (!target_view_)
+    return;
+
+  gfx::Point target_view_location(root_view_location);
+  View::ConvertPointToView(root_view_, target_view_, &target_view_location);
+  DropTargetEvent enter_event(data,
+                              target_view_location.x(),
+                              target_view_location.y(),
+                              drag_operation);
+  target_view_->OnDragEntered(enter_event);
+}
+
+int DropHelper::NotifyDragOver(const OSExchangeData& data,
+                               const gfx::Point& root_view_location,
+                               int drag_operation) {
+  if (!target_view_)
+    return DragDropTypes::DRAG_NONE;
+
+  gfx::Point target_view_location(root_view_location);
+  View::ConvertPointToView(root_view_, target_view_, &target_view_location);
+  DropTargetEvent enter_event(data,
+                              target_view_location.x(),
+                              target_view_location.y(),
+                              drag_operation);
+  return target_view_->OnDragUpdated(enter_event);
+}
+
+void DropHelper::NotifyDragExit() {
+  if (target_view_)
+    target_view_->OnDragExited();
+}
+
+}  // namespace views
diff --git a/views/widget/drop_helper.h b/views/widget/drop_helper.h
new file mode 100644
index 0000000..63bfa27
--- /dev/null
+++ b/views/widget/drop_helper.h
@@ -0,0 +1,104 @@
+// Copyright (c) 2006-2008 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 VIEWS_WIDGET_DROP_HELPER_H_
+#define VIEWS_WIDGET_DROP_HELPER_H_
+
+#include "base/basictypes.h"
+
+class OSExchangeData;
+
+namespace gfx {
+class Point;
+}  // namespace gfx
+
+namespace views {
+
+class RootView;
+class View;
+
+// DropHelper provides support for managing the view a drop is going to occur
+// at during dnd as well as sending the view the appropriate dnd methods.
+// DropHelper is intended to be used by a class that interacts with the system
+// drag and drop. The system class invokes OnDragOver as the mouse moves,
+// then either OnDragExit or OnDrop when the drop is done.
+class DropHelper {
+ public:
+  explicit DropHelper(RootView* root_view);
+  ~DropHelper();
+
+  // Current view drop events are targeted at, may be NULL.
+  View* target_view() const { return target_view_; }
+
+  // Returns the RootView the DropHelper was created with.
+  RootView* root_view() const { return root_view_; }
+
+  // Resets the target_view_ to NULL if it equals view.
+  //
+  // This is invoked when a View is removed from the RootView to make sure
+  // we don't target a view that was removed during dnd.
+  void ResetTargetViewIfEquals(View* view);
+
+  // Invoked when a the mouse is dragged over the root view during a drag and
+  // drop operation. This method returns a bitmask of the types in DragDropTypes
+  // for the target view. If no view wants the drop, DRAG_NONE is returned.
+  int OnDragOver(const OSExchangeData& data,
+                 const gfx::Point& root_view_location,
+                 int drag_operation);
+
+  // Invoked when a the mouse is dragged out of the root view during a drag and
+  // drop operation.
+  void OnDragExit();
+
+  // Invoked when the user drops data on the root view during a drag and drop
+  // operation. See OnDragOver for details on return type.
+  //
+  // NOTE: implementations must invoke OnDragOver before invoking this,
+  // supplying the return value from OnDragOver as the drag_operation.
+  int OnDrop(const OSExchangeData& data,
+             const gfx::Point& root_view_location,
+             int drag_operation);
+
+  // Calculates the target view for a drop given the specified location in
+  // the coordinate system of the rootview. This tries to avoid continually
+  // querying CanDrop by returning target_view_ if the mouse is still over
+  // target_view_.
+  View* CalculateTargetView(const gfx::Point& root_view_location,
+                            const OSExchangeData& data,
+                            bool check_can_drop);
+
+ private:
+  // Implementation of CalculateTargetView. If |deepest_view| is non-NULL it is
+  // set to the deepest descendant of the RootView that contains the point
+  // |root_view_location|
+  View* CalculateTargetViewImpl(const gfx::Point& root_view_location,
+                                const OSExchangeData& data,
+                                bool check_can_drop,
+                                View** deepest_view);
+
+  // Methods to send the appropriate drop notification to the targeted view.
+  // These do nothing if the target view is NULL.
+  void NotifyDragEntered(const OSExchangeData& data,
+                         const gfx::Point& root_view_location,
+                         int drag_operation);
+  int NotifyDragOver(const OSExchangeData& data,
+                     const gfx::Point& root_view_location,
+                     int drag_operation);
+  void NotifyDragExit();
+
+  // RootView we were created for.
+  RootView* root_view_;
+
+  // View we're targeting events at.
+  View* target_view_;
+
+  // The deepest view under the current drop coordinate.
+  View* deepest_view_;
+
+  DISALLOW_COPY_AND_ASSIGN(DropHelper);
+};
+
+}  // namespace views
+
+#endif  // VIEWS_WIDGET_DROP_HELPER_H_
diff --git a/views/widget/drop_target_win.cc b/views/widget/drop_target_win.cc
new file mode 100644
index 0000000..69800ca
--- /dev/null
+++ b/views/widget/drop_target_win.cc
@@ -0,0 +1,59 @@
+// Copyright (c) 2009 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.
+
+#include "views/widget/drop_target_win.h"
+
+#include "app/drag_drop_types.h"
+#include "app/os_exchange_data.h"
+#include "base/gfx/point.h"
+#include "views/widget/root_view.h"
+#include "views/widget/widget.h"
+
+namespace views {
+
+DropTargetWin::DropTargetWin(RootView* root_view)
+    : BaseDropTarget(root_view->GetWidget()->GetNativeView()),
+      helper_(root_view) {
+}
+
+DropTargetWin::~DropTargetWin() {
+}
+
+void DropTargetWin::ResetTargetViewIfEquals(View* view) {
+  helper_.ResetTargetViewIfEquals(view);
+}
+
+DWORD DropTargetWin::OnDragOver(IDataObject* data_object,
+                                DWORD key_state,
+                                POINT cursor_position,
+                                DWORD effect) {
+  gfx::Point root_view_location(cursor_position.x, cursor_position.y);
+  View::ConvertPointToView(NULL, helper_.root_view(), &root_view_location);
+  int drop_operation =
+      helper_.OnDragOver(OSExchangeData(data_object),
+                         root_view_location,
+                         DragDropTypes::DropEffectToDragOperation(effect));
+  return DragDropTypes::DragOperationToDropEffect(drop_operation);
+}
+
+void DropTargetWin::OnDragLeave(IDataObject* data_object) {
+  helper_.OnDragExit();
+}
+
+DWORD DropTargetWin::OnDrop(IDataObject* data_object,
+                            DWORD key_state,
+                            POINT cursor_position,
+                            DWORD effect) {
+  gfx::Point root_view_location(cursor_position.x, cursor_position.y);
+  View::ConvertPointToView(NULL, helper_.root_view(), &root_view_location);
+
+  OSExchangeData data(data_object);
+  int drop_operation = DragDropTypes::DropEffectToDragOperation(effect);
+  drop_operation = helper_.OnDragOver(data, root_view_location,
+                                      drop_operation);
+  drop_operation = helper_.OnDrop(data, root_view_location, drop_operation);
+  return DragDropTypes::DragOperationToDropEffect(drop_operation);
+}
+
+}  // namespace views
diff --git a/views/widget/drop_target_win.h b/views/widget/drop_target_win.h
new file mode 100644
index 0000000..d771c07
--- /dev/null
+++ b/views/widget/drop_target_win.h
@@ -0,0 +1,53 @@
+// Copyright (c) 2009 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 VIEWS_WIDGET_DROP_TARGET_WIN_H_
+#define VIEWS_WIDGET_DROP_TARGET_WIN_H_
+
+#include "base/base_drop_target.h"
+#include "views/widget/drop_helper.h"
+
+namespace views {
+
+class RootView;
+class View;
+
+// DropTargetWin takes care of managing drag and drop for WidgetWin. It
+// converts Windows OLE drop messages into Views drop messages.
+//
+// DropTargetWin uses DropHelper to manage the appropriate view to target
+// drop messages at.
+class DropTargetWin : public BaseDropTarget {
+ public:
+  explicit DropTargetWin(RootView* root_view);
+  virtual ~DropTargetWin();
+
+  // If a drag and drop is underway and view is the current drop target, the
+  // drop target is set to null.
+  // This is invoked when a View is removed from the RootView to make sure
+  // we don't target a view that was removed during dnd.
+  void ResetTargetViewIfEquals(View* view);
+
+ protected:
+  virtual DWORD OnDragOver(IDataObject* data_object,
+                           DWORD key_state,
+                           POINT cursor_position,
+                           DWORD effect);
+
+  virtual void OnDragLeave(IDataObject* data_object);
+
+  virtual DWORD OnDrop(IDataObject* data_object,
+                       DWORD key_state,
+                       POINT cursor_position,
+                       DWORD effect);
+
+ private:
+  views::DropHelper helper_;
+
+  DISALLOW_COPY_AND_ASSIGN(DropTargetWin);
+};
+
+}  // namespace views
+
+#endif  // VIEWS_WIDGET_DROP_TARGET_WIN_H_
diff --git a/views/widget/root_view.cc b/views/widget/root_view.cc
index 145de92..526e6d1 100644
--- a/views/widget/root_view.cc
+++ b/views/widget/root_view.cc
@@ -15,11 +15,6 @@
 #include "views/widget/widget.h"
 #include "views/window/window.h"
 
-#if defined(OS_WIN)
-#include "base/base_drag_source.h"
-#include "views/widget/root_view_drop_target.h"
-#endif
-
 namespace views {
 
 /////////////////////////////////////////////////////////////////////////////
@@ -257,12 +252,8 @@ void RootView::ViewHierarchyChanged(bool is_add, View* parent, View* child) {
       mouse_pressed_handler_ = NULL;
     }
 
-#if defined(OS_WIN)
-    if (drop_target_.get())
-      drop_target_->ResetTargetViewIfEquals(child);
-#else
-    NOTIMPLEMENTED();
-#endif
+    if (widget_)
+      widget_->ViewHierarchyChanged(is_add, parent, child);
 
     if (mouse_move_handler_ == child) {
       mouse_move_handler_ = NULL;
@@ -507,28 +498,6 @@ void RootView::SetMouseHandler(View *new_mh) {
   mouse_pressed_handler_ = new_mh;
 }
 
-void RootView::OnWidgetCreated() {
-#if defined(OS_WIN)
-  DCHECK(!drop_target_.get());
-  drop_target_ = new RootViewDropTarget(this);
-#else
-  // TODO(port): Port RootViewDropTarget and this goes away.
-  NOTIMPLEMENTED();
-#endif
-}
-
-void RootView::OnWidgetDestroyed() {
-#if defined(OS_WIN)
-  if (drop_target_.get()) {
-    RevokeDragDrop(GetWidget()->GetNativeView());
-    drop_target_ = NULL;
-  }
-#else
-  // TODO(port): Port RootViewDropTarget and this goes away.
-  NOTIMPLEMENTED();
-#endif
-}
-
 void RootView::ProcessMouseDragCanceled() {
   if (mouse_pressed_handler_) {
     // Synthesize a release event.
diff --git a/views/widget/root_view.h b/views/widget/root_view.h
index 8e8d467..b3c43d8 100644
--- a/views/widget/root_view.h
+++ b/views/widget/root_view.h
@@ -18,7 +18,6 @@ typedef struct _GdkEventExpose GdkEventExpose;
 namespace views {
 
 class PaintTask;
-class RootViewDropTarget;
 class Widget;
 
 /////////////////////////////////////////////////////////////////////////////
@@ -92,14 +91,6 @@ class RootView : public View,
   virtual void OnMouseMoved(const MouseEvent& e);
   virtual void SetMouseHandler(View* new_mouse_handler);
 
-  // Invoked when the Widget has been fully initialized.
-  // At the time the constructor is invoked the Widget may not be completely
-  // initialized, when this method is invoked, it is.
-  void OnWidgetCreated();
-
-  // Invoked prior to the Widget being destroyed.
-  void OnWidgetDestroyed();
-
   // Invoked By the Widget if the mouse drag is interrupted by
   // the system. Invokes OnMouseReleased with a value of true for canceled.
   void ProcessMouseDragCanceled();
@@ -326,11 +317,6 @@ class RootView : public View,
   // wrapped inside native components, and is used for the focus traversal.
   View* focus_traversable_parent_view_;
 
-#if defined(OS_WIN)
-  // Handles dnd for us.
-  scoped_refptr<RootViewDropTarget> drop_target_;
-#endif
-
   // Storage of strings needed for accessibility.
   std::wstring accessible_name_;
 
diff --git a/views/widget/root_view_drop_target.cc b/views/widget/root_view_drop_target.cc
deleted file mode 100644
index 9c1f087..0000000
--- a/views/widget/root_view_drop_target.cc
+++ /dev/null
@@ -1,118 +0,0 @@
-// Copyright (c) 2006-2008 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.
-
-#include "views/widget/root_view_drop_target.h"
-
-#include "app/drag_drop_types.h"
-#include "base/gfx/point.h"
-#include "views/widget/root_view.h"
-#include "views/widget/widget.h"
-
-namespace views {
-
-RootViewDropTarget::RootViewDropTarget(RootView* root_view)
-    : BaseDropTarget(root_view->GetWidget()->GetNativeView()),
-      root_view_(root_view),
-      target_view_(NULL),
-      deepest_view_(NULL) {
-}
-
-RootViewDropTarget::~RootViewDropTarget() {
-}
-
-void RootViewDropTarget::ResetTargetViewIfEquals(View* view) {
-  if (target_view_ == view)
-    target_view_ = NULL;
-  if (deepest_view_ == view)
-    deepest_view_ = NULL;
-}
-
-DWORD RootViewDropTarget::OnDragOver(IDataObject* data_object,
-                                     DWORD key_state,
-                                     POINT cursor_position,
-                                     DWORD effect) {
-  const OSExchangeData data(data_object);
-  gfx::Point root_view_location(cursor_position.x, cursor_position.y);
-  View::ConvertPointToView(NULL, root_view_, &root_view_location);
-  View* view = CalculateTargetView(root_view_location, data);
-
-  if (view != target_view_) {
-    // Target changed notify old drag exited, then new drag entered.
-    if (target_view_)
-      target_view_->OnDragExited();
-    target_view_ = view;
-    if (target_view_) {
-      gfx::Point target_view_location(root_view_location);
-      View::ConvertPointToView(root_view_, target_view_, &target_view_location);
-      DropTargetEvent enter_event(data,
-          target_view_location.x(),
-          target_view_location.y(),
-          DragDropTypes::DropEffectToDragOperation(effect));
-      target_view_->OnDragEntered(enter_event);
-    }
-  }
-
-  if (target_view_) {
-    gfx::Point target_view_location(root_view_location);
-    View::ConvertPointToView(root_view_, target_view_, &target_view_location);
-    DropTargetEvent enter_event(data,
-        target_view_location.x(),
-        target_view_location.y(),
-        DragDropTypes::DropEffectToDragOperation(effect));
-    int result_operation = target_view_->OnDragUpdated(enter_event);
-    return DragDropTypes::DragOperationToDropEffect(result_operation);
-  } else {
-    return DROPEFFECT_NONE;
-  }
-}
-
-void RootViewDropTarget::OnDragLeave(IDataObject* data_object) {
-  if (target_view_)
-    target_view_->OnDragExited();
-  deepest_view_ = target_view_ = NULL;
-}
-
-DWORD RootViewDropTarget::OnDrop(IDataObject* data_object,
-                                 DWORD key_state,
-                                 POINT cursor_position,
-                                 DWORD effect) {
-  const OSExchangeData data(data_object);
-  DWORD drop_effect = OnDragOver(data_object, key_state, cursor_position,
-                                 effect);
-  View* drop_view = target_view_;
-  deepest_view_ = target_view_ = NULL;
-  if (drop_effect != DROPEFFECT_NONE) {
-    gfx::Point view_location(cursor_position.x, cursor_position.y);
-    View::ConvertPointToView(NULL, drop_view, &view_location);
-    DropTargetEvent drop_event(data, view_location.x(), view_location.y(),
-        DragDropTypes::DropEffectToDragOperation(effect));
-    return DragDropTypes::DragOperationToDropEffect(
-        drop_view->OnPerformDrop(drop_event));
-  } else {
-    if (drop_view)
-      drop_view->OnDragExited();
-    return DROPEFFECT_NONE;
-  }
-}
-
-View* RootViewDropTarget::CalculateTargetView(
-    const gfx::Point& root_view_location,
-    const OSExchangeData& data) {
-  View* view = root_view_->GetViewForPoint(root_view_location);
-  if (view == deepest_view_) {
-    // The view the mouse is over hasn't changed; reuse the target.
-    return target_view_;
-  }
-  // View under mouse changed, which means a new view may want the drop.
-  // Walk the tree, stopping at target_view_ as we know it'll accept the
-  // drop.
-  deepest_view_ = view;
-  while (view && view != target_view_ &&
-         (!view->IsEnabled() || !view->CanDrop(data))) {
-    view = view->GetParent();
-  }
-  return view;
-}
-
-}  // namespace views
diff --git a/views/widget/root_view_drop_target.h b/views/widget/root_view_drop_target.h
deleted file mode 100644
index 32cb14b..0000000
--- a/views/widget/root_view_drop_target.h
+++ /dev/null
@@ -1,71 +0,0 @@
-// Copyright (c) 2006-2008 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 VIEWS_WIDGET_ROOT_VIEW_DROP_TARGET_H_
-#define VIEWS_WIDGET_ROOT_VIEW_DROP_TARGET_H_
-
-#include "app/os_exchange_data.h"
-#include "base/base_drop_target.h"
-
-namespace gfx {
-class Point;
-}
-
-namespace views {
-
-class RootView;
-class View;
-
-// RootViewDropTarget takes care of managing drag and drop for the RootView and
-// converts Windows OLE drop messages into Views drop messages.
-//
-// RootViewDropTarget is responsible for determining the appropriate View to
-// use during a drag and drop session, and forwarding events to it.
-class RootViewDropTarget : public BaseDropTarget {
- public:
-  explicit RootViewDropTarget(RootView* root_view);
-  virtual ~RootViewDropTarget();
-
-  // If a drag and drop is underway and view is the current drop target, the
-  // drop target is set to null.
-  // This is invoked when a View is removed from the RootView to make sure
-  // we don't target a view that was removed during dnd.
-  void ResetTargetViewIfEquals(View* view);
-
- protected:
-  virtual DWORD OnDragOver(IDataObject* data_object,
-                           DWORD key_state,
-                           POINT cursor_position,
-                           DWORD effect);
-
-  virtual void OnDragLeave(IDataObject* data_object);
-
-  virtual DWORD OnDrop(IDataObject* data_object,
-                       DWORD key_state,
-                       POINT cursor_position,
-                       DWORD effect);
-
- private:
-  // Calculates the target view for a drop given the specified location in
-  // the coordinate system of the rootview. This tries to avoid continually
-  // querying CanDrop by returning target_view_ if the mouse is still over
-  // target_view_.
-  View* CalculateTargetView(const gfx::Point& root_view_location,
-                            const OSExchangeData& data);
-
-  // RootView we were created for.
-  RootView* root_view_;
-
-  // View we're targeting events at.
-  View* target_view_;
-
-  // The deepest view under the current drop coordinate.
-  View* deepest_view_;
-
-  DISALLOW_EVIL_CONSTRUCTORS(RootViewDropTarget);
-};
-
-}  // namespace views
-
-#endif  // VIEWS_WIDGET_ROOT_VIEW_DROP_TARGET_H_
diff --git a/views/widget/root_view_win.cc b/views/widget/root_view_win.cc
index eddbb6e..fedb40d 100644
--- a/views/widget/root_view_win.cc
+++ b/views/widget/root_view_win.cc
@@ -8,7 +8,6 @@
 #include "app/gfx/canvas_paint.h"
 #include "base/base_drag_source.h"
 #include "base/logging.h"
-#include "views/widget/root_view_drop_target.h"
 
 namespace views {
 
diff --git a/views/widget/widget.h b/views/widget/widget.h
index f9e961d..829a9d0f 100644
--- a/views/widget/widget.h
+++ b/views/widget/widget.h
@@ -143,6 +143,10 @@ class Widget {
   // Returns the FocusManager for this widget.
   // Note that all widgets in a widget hierarchy share the same focus manager.
   virtual FocusManager* GetFocusManager() { return NULL; }
+
+  // Forwarded from the RootView so that the widget can do any cleanup.
+  virtual void ViewHierarchyChanged(bool is_add, View *parent,
+                                    View *child) = 0;
 };
 
 }  // namespace views
diff --git a/views/widget/widget_gtk.cc b/views/widget/widget_gtk.cc
index 76abe93..82af746 100644
--- a/views/widget/widget_gtk.cc
+++ b/views/widget/widget_gtk.cc
@@ -388,6 +388,12 @@ FocusManager* WidgetGtk::GetFocusManager() {
   return focus_manager_.get();
 }
 
+void WidgetGtk::ViewHierarchyChanged(bool is_add, View *parent,
+                                     View *child) {
+  // Needs dnd support (see WidgetWin::ViewHierarchyChanged).
+  NOTIMPLEMENTED();
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // WidgetGtk, MessageLoopForUI::Observer implementation:
 
diff --git a/views/widget/widget_gtk.h b/views/widget/widget_gtk.h
index 42ea283..b3308c4 100644
--- a/views/widget/widget_gtk.h
+++ b/views/widget/widget_gtk.h
@@ -96,6 +96,8 @@ class WidgetGtk : public Widget, public MessageLoopForUI::Observer {
   virtual const Window* GetWindow() const;
   virtual ThemeProvider* GetThemeProvider() const;
   virtual FocusManager* GetFocusManager();
+  virtual void ViewHierarchyChanged(bool is_add, View *parent,
+                                    View *child);
 
   // MessageLoopForUI::Observer.
   virtual void WillProcessEvent(GdkEvent* event);
diff --git a/views/widget/widget_win.cc b/views/widget/widget_win.cc
index 6a7b787..f431fc7 100644
--- a/views/widget/widget_win.cc
+++ b/views/widget/widget_win.cc
@@ -17,6 +17,7 @@
 #include "views/views_delegate.h"
 #include "views/widget/aero_tooltip_manager.h"
 #include "views/widget/default_theme_provider.h"
+#include "views/widget/drop_target_win.h"
 #include "views/widget/root_view.h"
 #include "views/window/window_win.h"
 
@@ -78,7 +79,7 @@ void WidgetWin::Init(gfx::NativeView parent, const gfx::Rect& bounds) {
 
   SetWindowSupportsRerouteMouseWheel(GetNativeView());
 
-  root_view_->OnWidgetCreated();
+  drop_target_ = new DropTargetWin(root_view_.get());
 
   if ((window_style() & WS_CHILD) == 0) {
     // Top-level widgets get a FocusManager.
@@ -320,6 +321,12 @@ FocusManager* WidgetWin::GetFocusManager() {
   return NULL;
 }
 
+void WidgetWin::ViewHierarchyChanged(bool is_add, View *parent,
+                                     View *child) {
+  if (drop_target_.get())
+    drop_target_->ResetTargetViewIfEquals(child);
+}
+
 void WidgetWin::SetUseLayeredBuffer(bool use_layered_buffer) {
   if (use_layered_buffer_ == use_layered_buffer)
     return;
@@ -432,7 +439,10 @@ void WidgetWin::OnClose() {
 }
 
 void WidgetWin::OnDestroy() {
-  root_view_->OnWidgetDestroyed();
+  if (drop_target_.get()) {
+    RevokeDragDrop(GetNativeView());
+    drop_target_ = NULL;
+  }
 
   RemoveProp(GetNativeView(), kRootViewWindowProperty);
 }
diff --git a/views/widget/widget_win.h b/views/widget/widget_win.h
index 49be8ea..3fbcc93 100644
--- a/views/widget/widget_win.h
+++ b/views/widget/widget_win.h
@@ -24,6 +24,7 @@ class Rect;
 
 namespace views {
 
+class DropTargetWin;
 class RootView;
 class TooltipManagerWin;
 class DefaultThemeProvider;
@@ -201,6 +202,8 @@ class WidgetWin : public base::WindowImpl,
   virtual Window* GetWindow();
   virtual const Window* GetWindow() const;
   virtual FocusManager* GetFocusManager();
+  virtual void ViewHierarchyChanged(bool is_add, View *parent,
+                                    View *child);
 
   // Overridden from MessageLoop::Observer:
   void WillProcessMessage(const MSG& msg);
@@ -485,6 +488,8 @@ class WidgetWin : public base::WindowImpl,
   // must be destroyed AFTER root_view_.
   scoped_ptr<TooltipManagerWin> tooltip_manager_;
 
+  scoped_refptr<DropTargetWin> drop_target_;
+
   // The focus manager keeping track of focus for this Widget and any of its
   // children.  NULL for non top-level widgets.
   // WARNING: RootView's destructor calls into the FocusManager. As such, this