PlzNavigate: properly execute BeforeUnload on renderer initiated navigations

third_party/WebKit/public/web/WebLocalFrame.h

Index: third_party/WebKit/public/web/WebLocalFrame.h
diff --git a/third_party/WebKit/public/web/WebLocalFrame.h b/third_party/WebKit/public/web/WebLocalFrame.h
index 7dd32559f963276187c6abdf5c307cec2696d570..1620f56ac2a40a14c3296e6b9fb0b57fe7c0370a 100644
--- a/third_party/WebKit/public/web/WebLocalFrame.h
+++ b/third_party/WebKit/public/web/WebLocalFrame.h
@@ -86,6 +86,11 @@ public:
 
     // Navigation ----------------------------------------------------------
 
+    // Runs beforeunload handlers for this frame and returns the value returned
+    // by handlers.
+    // Note: this may lead to the destruction of the frame.
+    virtual bool dispatchBeforeUnloadEvent(bool isReload) = 0;
+
     // Returns a WebURLRequest corresponding to the load of the WebHistoryItem.
     virtual WebURLRequest requestFromHistoryItem(const WebHistoryItem&, WebCachePolicy) const = 0;