Allow themes to change the background of the new tab page....

app/theme_provider.h

 // 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 APP_THEME_PROVIDER_H_
 #define APP_THEME_PROVIDER_H_
 
 #include "base/basictypes.h"
 #include "third_party/skia/include/core/SkColor.h"
 
@@ skipping 16 matching lines @@
  public:
   virtual ~ThemeProvider() { }
 
   // Get the bitmap specified by |id|. An implementation of ThemeProvider should
   // have its own source of ids (e.g. an enum, or external resource bundle).
   virtual SkBitmap* GetBitmapNamed(int id) = 0;
 
   // Get the color specified by |id|.
   virtual SkColor GetColor(int id) = 0;
 
+  // Get the property (e.g. an alignment expressed in an enum, or a width or
+  // height) specified by |id|.
+  virtual bool GetDisplayProperty(int id, int* result) = 0;
+
   // Whether we should use the native system frame (typically Aero glass) or
   // a custom frame.
   virtual bool ShouldUseNativeFrame() = 0;
 
 #if defined(OS_LINUX) && !defined(TOOLKIT_VIEWS)
   // Gets the GdkPixbuf with the specified |id|.  Returns a pointer to a shared
   // instance of the GdkPixbuf.  This shared GdkPixbuf is owned by the theme
   // provider and should not be freed.
   //
   // The bitmap is assumed to exist. This function will log in release, and
   // assert in debug mode if it does not. On failure, this will return a
   // pointer to a shared empty placeholder bitmap so it will be visible what
   // is missing.
   virtual GdkPixbuf* GetPixbufNamed(int id) = 0;
 #endif
 };
 
 #endif  // APP_THEME_PROVIDER_H_