Add 'didDispatchPingLoader' callback to FrameLoaderClient.

public/web/WebFrameClient.h

Index: public/web/WebFrameClient.h
diff --git a/public/web/WebFrameClient.h b/public/web/WebFrameClient.h
index 292ded1caeb4aa3aae92dfe867b0999e19e22946..e15ed3574691ffa6dfe5ac1f1f0e33840fdd6c2f 100644
--- a/public/web/WebFrameClient.h
+++ b/public/web/WebFrameClient.h
@@ -253,6 +253,9 @@ public:
     // A reflected XSS was encountered in the page and suppressed.
     virtual void didDetectXSS(WebFrame*, const WebURL&, bool didBlockEntirePage) { }
 
+    // A PingLoader was created, and a request dispatched to a URL.
+    virtual void didDispatchPingLoader(WebFrame*, const WebURL&) { }
+
     // Script notifications ------------------------------------------------
 
     // Script in the page tried to allocate too much memory.