Combine tab background image getter code into one place.

chrome/browser/ui/views/tabs/tab_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_VIEWS_TABS_TAB_STRIP_H_
 #define CHROME_BROWSER_UI_VIEWS_TABS_TAB_STRIP_H_
 
 #include <vector>
 
 #include "base/compiler_specific.h"
@@ skipping 213 matching lines @@
       Tab* tab,
       const ui::LocatedEvent& event,
       const ui::ListSelectionModel& original_selection) override;
   void ContinueDrag(views::View* view, const ui::LocatedEvent& event) override;
   bool EndDrag(EndDragReason reason) override;
   Tab* GetTabAt(Tab* tab, const gfx::Point& tab_in_tab_coordinates) override;
   void OnMouseEventInTab(views::View* source,
                          const ui::MouseEvent& event) override;
   bool ShouldPaintTab(const Tab* tab, gfx::Rect* clip) override;
   bool IsImmersiveStyle() const override;
+  int GetBackgroundResourceId(bool* custom_image) const override;
   void UpdateTabAccessibilityState(const Tab* tab,
                                    ui::AXViewState* state) override;
 
   // MouseWatcherListener overrides:
   void MouseMovedOutOfHost() override;
 
   // views::View overrides:
   void Layout() override;
   void PaintChildren(const ui::PaintContext& context) override;
   const char* GetClassName() const override;
@@ skipping 401 matching lines @@
   bool immersive_style_;
 
   // Our observers.
   typedef base::ObserverList<TabStripObserver> TabStripObservers;
   TabStripObservers observers_;
 
   DISALLOW_COPY_AND_ASSIGN(TabStrip);
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_TABS_TAB_STRIP_H_