Move MainWorldScriptContext accessor/method from WebFrame to WebLocalFrame.

extensions/renderer/extension_helper.cc

Index: extensions/renderer/extension_helper.cc
diff --git a/extensions/renderer/extension_helper.cc b/extensions/renderer/extension_helper.cc
index d90a34d7066fcc1186acd604aed54accda9a574f..eb64c4b6a4eba472956b4f990b379aa62528d16d 100644
--- a/extensions/renderer/extension_helper.cc
+++ b/extensions/renderer/extension_helper.cc
@@ -15,6 +15,7 @@
 #include "extensions/renderer/dispatcher.h"
 #include "third_party/WebKit/public/platform/WebURLRequest.h"
 #include "third_party/WebKit/public/web/WebDocument.h"
+#include "third_party/WebKit/public/web/WebLocalFrame.h"
 #include "third_party/WebKit/public/web/WebView.h"
 
 namespace extensions {
@@ -66,9 +67,16 @@ void ExtensionHelper::OnSetFrameName(const std::string& name) {
 }
 
 void ExtensionHelper::OnAppWindowClosed() {
+  // ExtensionMsg_AppWindowClosed is always sent to the current, non-swapped-out
+  // RenderView where the main frame is a local frame.
+  DCHECK(render_view()->GetWebView()->MainFrame()->IsWebLocalFrame());
+
   v8::HandleScope scope(v8::Isolate::GetCurrent());
-  v8::Local<v8::Context> v8_context =
-      render_view()->GetWebView()->MainFrame()->MainWorldScriptContext();
+  v8::Local<v8::Context> v8_context = render_view()
+                                          ->GetWebView()
+                                          ->MainFrame()
+                                          ->ToWebLocalFrame()
+                                          ->MainWorldScriptContext();
   ScriptContext* script_context =
       dispatcher_->script_context_set().GetByV8Context(v8_context);
   if (!script_context)