Cleanup to keep panel from manipulating its panel strip assignment directly.

chrome/browser/ui/panels/panel_strip.h

 // Copyright (c) 2012 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 CHROME_BROWSER_UI_PANELS_PANEL_STRIP_H_
 #define CHROME_BROWSER_UI_PANELS_PANEL_STRIP_H_
 #pragma once
 
 #include "ui/gfx/rect.h"
 
@@ skipping 18 matching lines @@
 
   // Updates the positioning of all panels in the collection, usually as
   // a result of removing or resizing a panel in collection.
   virtual void RefreshLayout() = 0;
 
   // Adds |panel| to the collection of panels.
   virtual void AddPanel(Panel* panel) = 0;
 
   // Removes |panel| from the collection of panels. Invoked asynchronously
   // after a panel has been closed.
-  // Returns |false| if the panel is not in the strip.
-  virtual bool RemovePanel(Panel* panel) = 0;
+  virtual void RemovePanel(Panel* panel) = 0;
 
   // Closes all panels in the collection. Panels will be removed after closing.
   virtual void CloseAll() = 0;
 
   // Resizes the |panel| to the |preferred_window_size| and updates the layout
   // of other panels in the collection accordingly.
   // |preferred_window_size| is the outer dimensions of the window, not
   // the content area, and is in screen coordinates.
   // The preferred size may be adjusted to fit layout constraints.
   virtual void ResizePanelWindow(Panel* panel,
@@ skipping 25 matching lines @@
   virtual void EndDraggingPanel(Panel* panel, bool cancelled) = 0;
 
  protected:
   explicit PanelStrip(Type type);
   virtual ~PanelStrip();
 
   const Type type_;  // Type of this panel strip.
 };
 
 #endif  // CHROME_BROWSER_UI_PANELS_PANEL_STRIP_H_