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

chrome/browser/ui/panels/panel_host.cc

Index: chrome/browser/ui/panels/panel_host.cc
===================================================================
--- chrome/browser/ui/panels/panel_host.cc	(revision 154307)
+++ chrome/browser/ui/panels/panel_host.cc	(working copy)
@@ -109,7 +109,7 @@
     panel_->UpdateTitleBar();
 }
 
-void PanelHost::AddNewContents(content::WebContents* source,
+bool PanelHost::AddNewContents(content::WebContents* source,
                                content::WebContents* new_contents,
                                WindowOpenDisposition disposition,
                                const gfx::Rect& initial_pos,
@@ -132,6 +132,7 @@
   navigate_params.user_gesture = user_gesture;
   navigate_params.extension_app_id = panel_->extension_id();
   chrome::Navigate(&navigate_params);
+  return true;
 }
 
 void PanelHost::ActivateContents(content::WebContents* contents) {