Implement WebPrescientNetworking::prefetchDNS.

chrome/renderer/net/prescient_networking_dispatcher.h

Index: chrome/renderer/net/prescient_networking_dispatcher.h
diff --git a/chrome/renderer/net/prescient_networking_dispatcher.h b/chrome/renderer/net/prescient_networking_dispatcher.h
index 3a0e9ba984dcd9350f68dc846166f12096399748..85a77bd9487396582004fde57fd2e40d5eb4f54e 100644
--- a/chrome/renderer/net/prescient_networking_dispatcher.h
+++ b/chrome/renderer/net/prescient_networking_dispatcher.h
@@ -6,14 +6,22 @@
 #define CHROME_RENDERER_NET_PRESCIENT_NETWORKING_DISPATCHER_H_
 
 #include "base/compiler_specific.h"
+#include "chrome/renderer/net/renderer_net_predictor.h"
 #include "third_party/WebKit/public/platform/WebPrescientNetworking.h"
 
 class PrescientNetworkingDispatcher : public WebKit::WebPrescientNetworking {
  public:
+  PrescientNetworkingDispatcher();
   virtual ~PrescientNetworkingDispatcher();
 
+  virtual void prefetchDNS(const WebKit::WebString& hostname) OVERRIDE;
+
   virtual void preconnect(const WebKit::WebURL& url,
                           WebKit::WebPreconnectMotivation motivation) OVERRIDE;
+ private:
+  RendererNetPredictor net_predictor_;
+
+  DISALLOW_COPY_AND_ASSIGN(PrescientNetworkingDispatcher);
 };
 
 #endif  // CHROME_RENDERER_NET_PRESCIENT_NETWORKING_DISPATCHER_H_