Attempt 2 at:

views/widget/root_view.h

 // Copyright (c) 2010 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_H_
 #define VIEWS_WIDGET_ROOT_VIEW_H_
 
+#include <set>
 #include <string>
 
 #include "base/ref_counted.h"
 #include "views/focus/focus_manager.h"
 #include "views/view.h"
 
 #if defined(OS_LINUX)
 typedef struct _GdkEventExpose GdkEventExpose;
 #endif
 
@@ skipping 192 matching lines @@
 
   // Notification that size and/or position of a view has changed. This
   // notifies the appropriate views.
   void ViewBoundsChanged(View* view, bool size_changed, bool position_changed);
 
   // Registers a view for notification when the visible bounds relative to the
   // root of a view changes.
   void RegisterViewForVisibleBoundsNotification(View* view);
   void UnregisterViewForVisibleBoundsNotification(View* view);
 
+  // Registers/unregisters the View for mouse near events.
+  void RegisterViewForNearNotification(View* view);
+  void UnregisterViewForNearNotification(View* view);
+
   // Returns the next focusable view or view containing a FocusTraversable (NULL
   // if none was found), starting at the starting_view.
   // check_starting_view, can_go_up and can_go_down controls the traversal of
   // the views hierarchy.
   // skip_group_id specifies a group_id, -1 means no group. All views from a
   // group are traversed in one pass.
   View* FindNextFocusableViewImpl(View* starting_view,
                                   bool check_starting_view,
                                   bool can_go_up,
                                   bool can_go_down,
@@ skipping 21 matching lines @@
 
   // Updates the last_mouse_* fields from e.
   void SetMouseLocationAndFlags(const MouseEvent& e);
 
   // If a view is dragging, this returns it. Otherwise returns NULL.
   View* GetDragView();
 
   // Sets the current cursor, or resets it to the last one if NULL is provided.
   void SetActiveCursor(gfx::NativeCursor cursor);
 
+  // Returns in |near_views| the set of views registered for mouse near events
+  // that overlap with the location of the specified event.
+  void GetViewsRegisteredForNearNotification(const MouseEvent& e,
+                                             std::set<View*>* near_views);
+
+  // Sends OnMouseExitedNear to the set of views the mouse is near and empties
+  // the set.
+  void SendMouseExitedNear();
+
   // The view currently handing down - drag - up
   View* mouse_pressed_handler_;
 
   // The view currently handling enter / exit
   View* mouse_move_handler_;
 
   // The last view to handle a mouse click, so that we can determine if
   // a double-click lands on the same view as its single-click part.
   View* last_click_handler_;
 
@@ skipping 52 matching lines @@
 
   // Valid for the lifetime of StartDragForViewFromMouseEvent, indicates the
   // view the drag started from.
   View* drag_view_;
 
 #ifndef NDEBUG
   // True if we're currently processing paint.
   bool is_processing_paint_;
 #endif
 
+  // Set of views registered for mouse near events.
+  // NOTE: because views registered for near mouse events can overlap other
+  // views and extend outside the bounds of themselves and ancestors we store
+  // the registered views here and treat them separately. This is generally ok
+  // as there are a small set of views registered for near notification.
+  std::set<View*> registered_near_views_;
+
+  // Set of views the mouse is currently near.
+  std::set<View*> near_views_;
+
   DISALLOW_COPY_AND_ASSIGN(RootView);
 };
 
 }  // namespace views
 
 #endif  // VIEWS_WIDGET_ROOT_VIEW_H_