Don't use GetAsTabContents. Send notifications from TabContentsView instead.

chrome/browser/tab_contents/tab_contents_view.cc

Index: chrome/browser/tab_contents/tab_contents_view.cc
diff --git a/chrome/browser/tab_contents/tab_contents_view.cc b/chrome/browser/tab_contents/tab_contents_view.cc
index 47e71f2706af0ea586e542f3d912b7318775c200..25264f04b102904cecddd0904dd06e85c2bb7a61 100644
--- a/chrome/browser/tab_contents/tab_contents_view.cc
+++ b/chrome/browser/tab_contents/tab_contents_view.cc
@@ -11,6 +11,8 @@
 #include "chrome/browser/renderer_host/render_widget_host_view.h"
 #include "chrome/browser/tab_contents/tab_contents.h"
 #include "chrome/browser/tab_contents/tab_contents_delegate.h"
+#include "chrome/common/notification_service.h"
+#include "chrome/common/render_messages_params.h"
 
 TabContentsView::TabContentsView(TabContents* tab_contents)
     : tab_contents_(tab_contents) {
@@ -30,8 +32,7 @@ void TabContentsView::RenderViewCreated(RenderViewHost* host) {
 
 void TabContentsView::CreateNewWindow(
     int route_id,
-    WindowContainerType window_container_type,
-    const string16& frame_name) {
+    const ViewHostMsg_CreateWindow_Params& params) {
   TabContents* new_contents = delegate_view_helper_.CreateNewWindow(
       route_id,
       tab_contents_->profile(),
@@ -39,11 +40,18 @@ void TabContentsView::CreateNewWindow(
       DOMUIFactory::GetDOMUIType(tab_contents_->profile(),
           tab_contents_->GetURL()),
       tab_contents_,
-      window_container_type,
-      frame_name);
+      params.window_container_type,
+      params.frame_name);
 
-  if (new_contents && tab_contents_->delegate())
-    tab_contents_->delegate()->TabContentsCreated(new_contents);
+  if (new_contents) {
+    NotificationService::current()->Notify(
+        NotificationType::CREATING_NEW_WINDOW,
+        Source<TabContents>(tab_contents_),
+        Details<const ViewHostMsg_CreateWindow_Params>(&params));
+
+    if (tab_contents_->delegate())
+      tab_contents_->delegate()->TabContentsCreated(new_contents);
+  }
 }
 
 void TabContentsView::CreateNewWidget(int route_id,