GTK: First draft of using native themes, partially based on evan's CL 118358.

chrome/browser/gtk/back_forward_button_gtk.h

Index: chrome/browser/gtk/back_forward_button_gtk.h
diff --git a/chrome/browser/gtk/back_forward_button_gtk.h b/chrome/browser/gtk/back_forward_button_gtk.h
index 693ff400e8753e92bc86dc7a6149bc8b0db80833..d63412f5f65649ec5f52c35a50732236e1b23b75 100644
--- a/chrome/browser/gtk/back_forward_button_gtk.h
+++ b/chrome/browser/gtk/back_forward_button_gtk.h
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef CHROME_BROWSER_GTK_BACK_FORWARD_BUTTON_GTK_
-#define CHROME_BROWSER_GTK_BACK_FORWARD_BUTTON_GTK_
+#ifndef CHROME_BROWSER_GTK_BACK_FORWARD_BUTTON_GTK_H_
+#define CHROME_BROWSER_GTK_BACK_FORWARD_BUTTON_GTK_H_
 
 #include "base/scoped_ptr.h"
 #include "base/task.h"
@@ -27,6 +27,9 @@ class BackForwardButtonGtk {
 
   GtkWidget* widget() { return button_->widget(); }
 
+  // Advises our CustomDrawButtons on how to render.
+  void SetUseSystemTheme(bool use_gtk);
+
  private:
   // Executes the browser command.
   static void OnClick(GtkWidget* widget, BackForwardButtonGtk* button);
@@ -75,4 +78,4 @@ class BackForwardButtonGtk {
   DISALLOW_COPY_AND_ASSIGN(BackForwardButtonGtk);
 };
 
-#endif  // CHROME_BROWSER_GTK_BACK_FORWARD_BUTTON_GTK_
+#endif  // CHROME_BROWSER_GTK_BACK_FORWARD_BUTTON_GTK_H_