Pass result of blockage across content API when new tab blocked.

ui/views/controls/webview/web_dialog_view.cc

Index: ui/views/controls/webview/web_dialog_view.cc
===================================================================
--- ui/views/controls/webview/web_dialog_view.cc	(revision 154307)
+++ ui/views/controls/webview/web_dialog_view.cc	(working copy)
@@ -277,16 +277,16 @@
   return WebDialogWebContentsDelegate::OpenURLFromTab(source, params);
 }
 
-void WebDialogView::AddNewContents(content::WebContents* source,
+bool WebDialogView::AddNewContents(content::WebContents* source,
                                    content::WebContents* new_contents,
                                    WindowOpenDisposition disposition,
                                    const gfx::Rect& initial_pos,
                                    bool user_gesture) {
   if (delegate_ && delegate_->HandleAddNewContents(
           source, new_contents, disposition, initial_pos, user_gesture)) {
-    return;
+    return true;
   }
-  WebDialogWebContentsDelegate::AddNewContents(
+  return WebDialogWebContentsDelegate::AddNewContents(
       source, new_contents, disposition, initial_pos, user_gesture);
 }