Tracing for NavigationHandle lifetime and state.

chrome/browser/page_load_metrics/metrics_navigation_throttle.h

 // Copyright 2016 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 CHROME_BROWSER_PAGE_LOAD_METRICS_METRICS_NAVIGATION_THROTTLE_H_
 #define CHROME_BROWSER_PAGE_LOAD_METRICS_METRICS_NAVIGATION_THROTTLE_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "content/public/browser/navigation_throttle.h"
 
 namespace page_load_metrics {
 
 // This class is used to forward calls to the MetricsWebContentsObserver.
 // Namely, WillStartRequest() is called on NavigationThrottles, but not on
 // WebContentsObservers. Data from the NavigationHandle accessed at this point
 // is used to obtain more reliable abort metrics (like page transition type).
 class MetricsNavigationThrottle : public content::NavigationThrottle {
  public:
   static std::unique_ptr<content::NavigationThrottle> Create(
       content::NavigationHandle* handle);
   ~MetricsNavigationThrottle() override;
 
   // content::NavigationThrottle:
   content::NavigationThrottle::ThrottleCheckResult WillStartRequest() override;
   content::NavigationThrottle::ThrottleCheckResult WillProcessResponse()
       override;
+  const char* GetNameForLogging() override;
 
  private:
   explicit MetricsNavigationThrottle(content::NavigationHandle* handle);
 
   DISALLOW_COPY_AND_ASSIGN(MetricsNavigationThrottle);
 };
 
 }  // namespace page_load_metrics
 
 #endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_METRICS_NAVIGATION_THROTTLE_H_