Make a clean interface for dialog callbacks.

chrome/browser/tab_contents/background_contents.cc

Index: chrome/browser/tab_contents/background_contents.cc
diff --git a/chrome/browser/tab_contents/background_contents.cc b/chrome/browser/tab_contents/background_contents.cc
index 5898b55d46755d2e3a60ba663eb0cc564f76579c..b7fa507f12e1c8e014fd0c0a40688cf46addb36c 100644
--- a/chrome/browser/tab_contents/background_contents.cc
+++ b/chrome/browser/tab_contents/background_contents.cc
@@ -150,14 +150,6 @@ gfx::NativeWindow BackgroundContents::GetDialogRootWindow() {
   return NULL;
 }
 
-TabContents* BackgroundContents::AsTabContents() {
-  return NULL;
-}
-
-ExtensionHost* BackgroundContents::AsExtensionHost() {
-  return NULL;
-}
-
 void BackgroundContents::UpdateInspectorSetting(const std::string& key,
                                          const std::string& value) {
   Profile* profile = render_view_host_->process()->profile();