Make shelf item can be dragged when context menu is opened.

ui/views/controls/menu/menu_controller.h

Index: ui/views/controls/menu/menu_controller.h
diff --git a/ui/views/controls/menu/menu_controller.h b/ui/views/controls/menu/menu_controller.h
index 16ac2d4bd9c3a746d667f5c2c41e45d186e6fe61..7c7c1e912c23886f137ceef2d8e3140a1ae71b2b 100644
--- a/ui/views/controls/menu/menu_controller.h
+++ b/ui/views/controls/menu/menu_controller.h
@@ -102,6 +102,15 @@ class VIEWS_EXPORT MenuController
   // is no drag in progress.
   bool did_initiate_drag() const { return did_initiate_drag_; }
 
+  bool preserve_current_gesture_for_owner() const {
+    return preserve_current_gesture_for_owner_;
+  }
+
+  void set_preserve_current_gesture_for_owner(
+      bool preserve_current_gesture_for_owner) {
+    preserve_current_gesture_for_owner_ = preserve_current_gesture_for_owner;
+  }
+
   // Returns the owner of child windows.
   // WARNING: this may be NULL.
   Widget* owner() { return owner_; }
@@ -560,14 +569,14 @@ class VIEWS_EXPORT MenuController
   bool blocking_run_;
 
   // If true, we're showing.
-  bool showing_;
+  bool showing_ = false;
 
   // Indicates what to exit.
-  ExitType exit_type_;
+  ExitType exit_type_ = EXIT_NONE;
 
   // Whether we did a capture. We do a capture only if we're blocking and
   // the mouse was down when Run.
-  bool did_capture_;
+  bool did_capture_ = false;
 
   // As the user drags the mouse around pending_state_ changes immediately.
   // When the user stops moving/dragging the mouse (or clicks the mouse)
@@ -579,10 +588,10 @@ class VIEWS_EXPORT MenuController
   State state_;
 
   // If the user accepted the selection, this is the result.
-  MenuItemView* result_;
+  MenuItemView* result_ = nullptr;
 
   // The event flags when the user selected the menu.
-  int accept_event_flags_;
+  int accept_event_flags_ = 0;
 
   // If not empty, it means we're nested. When Run is invoked from within
   // Run, the current state (state_) is pushed onto menu_stack_. This allows
@@ -607,35 +616,35 @@ class VIEWS_EXPORT MenuController
   base::OneShotTimer cancel_all_timer_;
 
   // Drop target.
-  MenuItemView* drop_target_;
-  MenuDelegate::DropPosition drop_position_;
+  MenuItemView* drop_target_ = nullptr;
+  MenuDelegate::DropPosition drop_position_ = MenuDelegate::DROP_UNKNOWN;
 
   // Owner of child windows.
   // WARNING: this may be NULL.
-  Widget* owner_;
+  Widget* owner_ = nullptr;
 
   // Indicates a possible drag operation.
-  bool possible_drag_;
+  bool possible_drag_ = false;
 
   // True when drag operation is in progress.
-  bool drag_in_progress_;
+  bool drag_in_progress_ = false;
 
   // True when the drag operation in progress was initiated by the
   // MenuController for a child MenuItemView (as opposed to initiated separately
   // by a child View).
-  bool did_initiate_drag_;
+  bool did_initiate_drag_ = false;
 
   // Location the mouse was pressed at. Used to detect d&d.
   gfx::Point press_pt_;
 
   // We get a slew of drag updated messages as the mouse is over us. To avoid
   // continually processing whether we can drop, we cache the coordinates.
-  bool valid_drop_coordinates_;
+  bool valid_drop_coordinates_ = false;
   gfx::Point drop_pt_;
-  int last_drop_operation_;
+  int last_drop_operation_ = MenuDelegate::DROP_UNKNOWN;
 
   // If true, we're in the middle of invoking ShowAt on a submenu.
-  bool showing_submenu_;
+  bool showing_submenu_ = false;
 
   // Task for scrolling the menu. If non-null indicates a scroll is currently
   // underway.
@@ -649,7 +658,7 @@ class VIEWS_EXPORT MenuController
   const int active_mouse_view_id_;
 
   // Current hot tracked child button if any.
-  CustomButton* hot_button_;
+  CustomButton* hot_button_ = nullptr;
 
   internal::MenuControllerDelegate* delegate_;
 
@@ -665,19 +674,25 @@ class VIEWS_EXPORT MenuController
 
   // Controls behavior differences between a combobox and other types of menu
   // (like a context menu).
-  bool is_combobox_;
+  bool is_combobox_ = false;
+
+  // Whether the menu |owner_| needs gesture events. When set to true menu

[msw, 2017/06/01 20:24:27]

nit: "true, the menu"

[minch1, 2017/06/23 23:13:03]

Done.

+  // will help preserve the gesture events of the |owner_| and then
+  // MenuController will forward the gesture events to |owner_| if
+  // no |ET_GESTURE_END| event been captured.
+  bool preserve_current_gesture_for_owner_ = false;

[msw, 2017/06/01 20:24:28]

nit: sorry to bikeshed, but how about "send_gesture_events_to_owner_"?

[minch1, 2017/06/23 23:13:03]

Done.

 
   // Set to true if the menu item was selected by touch.
-  bool item_selected_by_touch_;
+  bool item_selected_by_touch_ = false;
 
   // During mouse event handling, this is the RootView to forward mouse events
   // to. We need this, because if we forward one event to it (e.g., mouse
   // pressed), subsequent events (like dragging) should also go to it, even if
   // the mouse is no longer over the view.
-  MenuHostRootView* current_mouse_event_target_;
+  MenuHostRootView* current_mouse_event_target_ = nullptr;
 
   // A mask of the EventFlags for the mouse buttons currently pressed.
-  int current_mouse_pressed_state_;
+  int current_mouse_pressed_state_ = 0;
 
 #if defined(USE_AURA)
   std::unique_ptr<MenuPreTargetHandler> menu_pre_target_handler_;