Change Page::m_mainFrame to be a Frame.

Source/modules/geolocation/GeolocationController.cpp

Index: Source/modules/geolocation/GeolocationController.cpp
diff --git a/Source/modules/geolocation/GeolocationController.cpp b/Source/modules/geolocation/GeolocationController.cpp
index cb174270ca2b92fd0f61eade3a93316ea63cef29..e9e9e17d972acb9f1d9268f41a1e92b80c2a5f89 100644
--- a/Source/modules/geolocation/GeolocationController.cpp
+++ b/Source/modules/geolocation/GeolocationController.cpp
@@ -51,14 +51,14 @@ GeolocationController::GeolocationController(LocalFrame& frame, GeolocationClien
         m_inspectorAgent = geolocationAgent.get();
         frame.page()->inspectorController().registerModuleAgent(geolocationAgent.release());
     } else {
-        m_inspectorAgent = GeolocationController::from(frame.page()->mainFrame())->m_inspectorAgent;
+        m_inspectorAgent = GeolocationController::from(toLocalFrame(frame.page()->mainFrame()))->m_inspectorAgent;
     }
 
     m_inspectorAgent->AddController(this);
 
     if (!frame.isMainFrame()) {
         // internals.setGeolocationClientMock is per page.
-        GeolocationController* mainController = GeolocationController::from(frame.page()->mainFrame());
+        GeolocationController* mainController = GeolocationController::from(toLocalFrame(frame.page()->mainFrame()));
         if (mainController->hasClientForTest())
             setClientForTest(mainController->client());
     }