Adding DRP specfic UMA for FirstContentfulPaint

chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.h

Index: chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.h
diff --git a/chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.h b/chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.h
index 25b26f125180e5dbcf41b400f5d4162b9148b0fd..756e483dcf4915aff2b637dc6bb8716c8eacae77 100644
--- a/chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.h
+++ b/chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.h
@@ -10,24 +10,32 @@
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "chrome/browser/external_protocol/external_protocol_handler.h"
 #include "content/public/browser/resource_dispatcher_host_delegate.h"
 
 class DelayedResourceQueue;
 class DownloadRequestLimiter;
 
+namespace content {
+class ResourceContext;
+}
+
 namespace extensions {
 class UserScriptListener;
 }
 
+namespace net {
+class HostPortPair;
+}
+
 namespace safe_browsing {
 class SafeBrowsingService;
 }
 
 // Implements ResourceDispatcherHostDelegate. Currently used by the Prerender
 // system to abort requests and add to the load flags when a request begins.
 class ChromeResourceDispatcherHostDelegate
     : public content::ResourceDispatcherHostDelegate {
  public:
   ChromeResourceDispatcherHostDelegate();
@@ -79,20 +87,24 @@ class ChromeResourceDispatcherHostDelegate
                          IPC::Sender* sender) override;
   void OnRequestRedirected(const GURL& redirect_url,
                            net::URLRequest* request,
                            content::ResourceContext* resource_context,
                            content::ResourceResponse* response) override;
   void RequestComplete(net::URLRequest* url_request) override;
   bool ShouldEnableLoFiMode(
       const net::URLRequest& url_request,
       content::ResourceContext* resource_context) override;
 
+  bool UsedDataReductionProxy(
+      const net::HostPortPair& proxy_server,
+      content::ResourceContext* resource_context) override;
+
   // Called on the UI thread. Allows switching out the
   // ExternalProtocolHandler::Delegate for testing code.
   static void SetExternalProtocolHandlerDelegateForTesting(
       ExternalProtocolHandler::Delegate* delegate);
 
  private:
 #if defined(ENABLE_EXTENSIONS)
   struct StreamTargetInfo {
     std::string extension_id;
     std::string view_id;