Make a clean interface for dialog callbacks.

content/browser/tab_contents/tab_contents.cc

Index: content/browser/tab_contents/tab_contents.cc
diff --git a/content/browser/tab_contents/tab_contents.cc b/content/browser/tab_contents/tab_contents.cc
index 13fcd7c9200e3c4a1e24d854807be5f7c0b6294e..7d5a1393bd422cf3b1212e4a8d4e7c0f415b530f 100644
--- a/content/browser/tab_contents/tab_contents.cc
+++ b/content/browser/tab_contents/tab_contents.cc
@@ -1841,12 +1841,8 @@ gfx::NativeWindow TabContents::GetDialogRootWindow() {
   return view_->GetTopLevelNativeWindow();
 }
 
-TabContents* TabContents::AsTabContents() {
-  return this;
-}
-
-ExtensionHost* TabContents::AsExtensionHost() {
-  return NULL;
+void TabContents::OnDialogShown() {
+  Activate();
 }
 
 void TabContents::set_encoding(const std::string& encoding) {