Detach old frame on WebFrame::swap.

Source/core/loader/FrameLoader.h

Index: Source/core/loader/FrameLoader.h
diff --git a/Source/core/loader/FrameLoader.h b/Source/core/loader/FrameLoader.h
index 82b5b1d0fa8418561dc01d8e46e09650b1bee5db..1aae7db2ff17f2c00bdd134a6d2e6ae384321d12 100644
--- a/Source/core/loader/FrameLoader.h
+++ b/Source/core/loader/FrameLoader.h
@@ -156,6 +156,11 @@ public:
     void finishedParsing();
     void checkCompleted();
 
+    // This prepares the FrameLoader for the next commit. It will dispatch
+    // unload events, abort XHR requests and detach the document. Returns true
+    // if the frame is ready to receive the next commit, or false otherwise.
+    bool prepareForCommit();
+
     void commitProvisionalLoad();
 
     FrameLoaderStateMachine* stateMachine() const { return &m_stateMachine; }