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

chrome/browser/ui/views/tabs/tab_drag_controller.cc

Index: chrome/browser/ui/views/tabs/tab_drag_controller.cc
===================================================================
--- chrome/browser/ui/views/tabs/tab_drag_controller.cc	(revision 154307)
+++ chrome/browser/ui/views/tabs/tab_drag_controller.cc	(working copy)
@@ -557,7 +557,7 @@
     view_->Update();
 }
 
-void TabDragController::AddNewContents(WebContents* source,
+bool TabDragController::AddNewContents(WebContents* source,
                                        WebContents* new_contents,
                                        WindowOpenDisposition disposition,
                                        const gfx::Rect& initial_pos,
@@ -567,9 +567,10 @@
   // Theoretically could be called while dragging if the page tries to
   // spawn a window. Route this message back to the browser in most cases.
   if (source_tab_drag_data()->original_delegate) {
-    source_tab_drag_data()->original_delegate->AddNewContents(
+    return source_tab_drag_data()->original_delegate->AddNewContents(
         source, new_contents, disposition, initial_pos, user_gesture);
   }
+  return true;
 }
 
 void TabDragController::LoadingStateChanged(WebContents* source) {