Adding DRP specfic UMA for FirstContentfulPaint

content/public/browser/navigation_handle.h

Index: content/public/browser/navigation_handle.h
diff --git a/content/public/browser/navigation_handle.h b/content/public/browser/navigation_handle.h
index f8a3b5e02fda3d45e37658e55253a77c4d3740bf..4f69719f790ab97b72b0b188d0da47f68692c074 100644
--- a/content/public/browser/navigation_handle.h
+++ b/content/public/browser/navigation_handle.h
@@ -1,26 +1,28 @@
 // Copyright 2015 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 CONTENT_PUBLIC_BROWSER_NAVIGATION_HANDLE_H_
 #define CONTENT_PUBLIC_BROWSER_NAVIGATION_HANDLE_H_
 
+#include "base/supports_user_data.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/navigation_throttle.h"
 #include "content/public/common/referrer.h"
 #include "net/base/net_errors.h"
 #include "ui/base/page_transition_types.h"
 
 class GURL;
 
 namespace content {
+class NavigationUserData;
 class NavigationThrottle;
 class RenderFrameHost;
 class WebContents;
 
 // A NavigationHandle tracks information related to a single navigation.
 // NavigationHandles are provided to several WebContentsObserver methods to
 // allow observers to track specific navigations. Observers should clear any
 // references to a NavigationHandle at the time of
 // WebContentsObserver::DidFinishNavigation, just before the handle is
 // destroyed.
@@ -127,20 +129,22 @@ class CONTENT_EXPORT NavigationHandle {
 
   // Resumes a navigation that was previously deferred by a NavigationThrottle.
   virtual void Resume() = 0;
 
   // Cancels a navigation that was previously deferred by a NavigationThrottle.
   // |result| should be equal to NavigationThrottle::CANCEL or
   // NavigationThrottle::CANCEL_AND_IGNORE.
   virtual void CancelDeferredNavigation(
       NavigationThrottle::ThrottleCheckResult result) = 0;
 
+  virtual base::SupportsUserData::Data* GetUserData(const void* key) = 0;
+
   // Testing methods ----------------------------------------------------------
   //
   // The following methods should be used exclusively for writing unit tests.
 
   static scoped_ptr<NavigationHandle> CreateNavigationHandleForTesting(
       const GURL& url,
       RenderFrameHost* render_frame_host);
 
   // Registers a NavigationThrottle for tests. The throttle can
   // modify the request, pause the request or cancel the request. This will