Don't wait to notify client of spoof attempt if a modal dialog is created.

Source/core/page/PageGroupLoadDeferrer.cpp

Index: Source/core/page/PageGroupLoadDeferrer.cpp
diff --git a/Source/core/page/PageGroupLoadDeferrer.cpp b/Source/core/page/PageGroupLoadDeferrer.cpp
index 43f66cb48b59951092661ec28287ae5272fd195f..fec74c1d9dee1d19443f2fb0ff6c6d78ac146815 100644
--- a/Source/core/page/PageGroupLoadDeferrer.cpp
+++ b/Source/core/page/PageGroupLoadDeferrer.cpp
@@ -22,6 +22,7 @@
 #include "core/page/PageGroupLoadDeferrer.h"
 
 #include "core/dom/Document.h"
+#include "core/loader/FrameLoader.h"
 #include "core/page/Frame.h"
 #include "core/page/Page.h"
 #include "core/page/PageGroup.h"
@@ -42,6 +43,10 @@ PageGroupLoadDeferrer::PageGroupLoadDeferrer(Page* page, bool deferSelf)
             if (!otherPage->defersLoading()) {
                 m_deferredFrames.append(otherPage->mainFrame());
 
+                // Ensure that we notify the client if the initial empty document is accessed before showing anything
+                // modal, to prevent spoofs while the modal window or sheet is visible.
+                otherPage->mainFrame()->loader()->notifyIfInitialDocumentAccessed();
+
                 // This code is not logically part of load deferring, but we do not want JS code executed beneath modal
                 // windows or sheets, which is exactly when PageGroupLoadDeferrer is used.
                 for (Frame* frame = otherPage->mainFrame(); frame; frame = frame->tree()->traverseNext())