PlzNavigate: properly execute BeforeUnload on renderer initiated navigations

third_party/WebKit/public/web/WebLocalFrame.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef WebLocalFrame_h
 #define WebLocalFrame_h
 
 #include "WebFrame.h"
 #include "WebFrameLoadType.h"
 
@@ skipping 68 matching lines @@
     // optionally wrapping around.
     virtual WebLocalFrame* traversePreviousLocal(bool wrap) const = 0;
     virtual WebLocalFrame* traverseNextLocal(bool wrap) const = 0;
 
     // Navigation Ping --------------------------------------------------------
 
     virtual void sendPings(const WebURL& destinationURL) = 0;
 
     // Navigation ----------------------------------------------------------
 
+    // 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.
+    virtual bool dispatchBeforeUnloadEvent(bool* proceed) = 0;

[dcheng, 2016/05/03 06:51:59]

Rather than using a bool out param, I'd suggest just combining the meanings into
the return val.

return false => don't navigate, bail out immediately, frame might be destroyed
return true => ok to proceed

Alternatively, we can express the state with an enum, which might make the code
clearer but isn't really needed atm.

[clamy, 2016/05/03 13:17:09]

There is one case where we need to distinguish between the two: cross-site
navigations where the browser expect an IPC back with the return value of
BeforeUnload. So I went with the enum option.

+
     // Returns a WebURLRequest corresponding to the load of the WebHistoryItem.
     virtual WebURLRequest requestFromHistoryItem(const WebHistoryItem&, WebCachePolicy) const = 0;
 
     // Returns a WebURLRequest corresponding to the reload of the current
     // HistoryItem.
     virtual WebURLRequest requestForReload(WebFrameLoadType,
         const WebURL& overrideURL = WebURL()) const = 0;
 
     // Load the given URL. For history navigations, a valid WebHistoryItem
     // should be given, as well as a WebHistoryLoadType.
@@ skipping 229 matching lines @@
     // to call these on a WebLocalFrame.
     bool isWebLocalFrame() const override = 0;
     WebLocalFrame* toWebLocalFrame() override = 0;
     bool isWebRemoteFrame() const override = 0;
     WebRemoteFrame* toWebRemoteFrame() override = 0;
 };
 
 } // namespace blink
 
 #endif // WebLocalFrame_h