Ignore attempts to navigate once a provisional commit has gotten too far along.

Source/core/loader/FrameLoader.cpp

Index: Source/core/loader/FrameLoader.cpp
diff --git a/Source/core/loader/FrameLoader.cpp b/Source/core/loader/FrameLoader.cpp
index 48d220f6f91568247d524e6583d944382bd5d6cc..475c6eca3be96c3010ccc7a5edc2f0c93f462e4b 100644
--- a/Source/core/loader/FrameLoader.cpp
+++ b/Source/core/loader/FrameLoader.cpp
@@ -972,8 +972,11 @@ void FrameLoader::commitProvisionalLoad()
     // we need to abandon the current load.
     if (pdl != m_provisionalDocumentLoader)
         return;
-    if (m_documentLoader)
+
+    if (m_documentLoader) {
+        NavigationDisablerForBeforeUnload navigationDisabler;

[michaeln, 2015/06/03 00:51:50]

I have to rename the class still.

         m_documentLoader->detachFromFrame();
+    }
     // detachFromFrame() will abort XHRs that haven't completed, which can
     // trigger event listeners for 'abort'. These event listeners might detach
     // the frame.