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..30d38018cf122358a7d35f69828bb9b333c10f91 100644
--- a/third_party/WebKit/public/web/WebLocalFrame.h
+++ b/third_party/WebKit/public/web/WebLocalFrame.h
@@ -86,6 +86,17 @@ public:
 
     // Navigation ----------------------------------------------------------
 
+    enum class BeforeUnloadReturnValue {
+        Proceed,
+        DontProceed,
+        FrameDestroyed,
+    };
+
+    // Runs beforeunload handlers for this frame and updates |proceed| with the
+    // value returned by handlers. Returns false if the execution of
+    // BeforeUnload led to the destruction of the frame, true otherwise.

[dcheng, 2016/05/03 21:34:30]

Also, this comment should be updated.

[clamy, 2016/05/04 13:50:15]

Done.

+    virtual BeforeUnloadReturnValue dispatchBeforeUnloadEvent(bool isReload) = 0;
+
     // Returns a WebURLRequest corresponding to the load of the WebHistoryItem.
     virtual WebURLRequest requestFromHistoryItem(const WebHistoryItem&, WebCachePolicy) const = 0;