Fix FirstWebContentsProfiler not getting created when using session restore.

chrome/browser/metrics/first_web_contents_profiler.h

 // Copyright 2014 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_METRICS_FIRST_WEB_CONTENTS_PROFILER_H_
 #define CHROME_BROWSER_METRICS_FIRST_WEB_CONTENTS_PROFILER_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "content/public/browser/web_contents_observer.h"
 
 namespace content {
 class WebContents;
 }  // namespace content
 
 // Measures start up performance of the first active web contents.
 // This class is declared on all platforms, but only defined on non-Android
 // platforms. Android code should not call any non-trivial methods on this
 // class.
 class FirstWebContentsProfiler : public content::WebContentsObserver {
  public:
-  explicit FirstWebContentsProfiler(content::WebContents* web_contents);
+  // Creates a profiler for the active web contents. If there are multiple
+  // browsers, the first one is chosen. The resulting FirstWebContentsProfiler
+  // owns itself.
+  static void WebContentsStarted(content::WebContents* web_contents);
 
  private:
   // Reasons for which profiling is deemed complete. Logged in UMA (do not re-
   // order or re-assign).
   enum FinishReason {
     // All metrics were successfully gathered.
     DONE = 0,
     // Abandon if blocking UI was shown during startup.
     ABANDON_BLOCKING_UI = 1,
     // Abandon if the content is hidden (lowers scheduling priority).
     ABANDON_CONTENT_HIDDEN = 2,
     // Abandon if the content is destroyed.
     ABANDON_CONTENT_DESTROYED = 3,
     // Abandon if the WebContents navigates away from its initial page.
     ABANDON_NEW_NAVIGATION = 4,
     // Abandon if the WebContents fails to load (e.g. network error, etc.).
     ABANDON_NAVIGATION_ERROR = 5,
     ENUM_MAX
   };
-
+  explicit FirstWebContentsProfiler(content::WebContents* web_contents);
   ~FirstWebContentsProfiler() override = default;
 
   // content::WebContentsObserver:
   void DidFirstVisuallyNonEmptyPaint() override;
   void DocumentOnLoadCompletedInMainFrame() override;
   void DidStartNavigation(
       content::NavigationHandle* navigation_handle) override;
   void DidFinishNavigation(
       content::NavigationHandle* navigation_handle) override;
   void WasHidden() override;
@@ skipping 16 matching lines @@
   // Whether an attempt was made to collect the "MainNavigationStart" metric.
   bool collected_main_navigation_start_metric_;
 
   // Whether an attempt was made to collect the "MainNavigationFinished" metric.
   bool collected_main_navigation_finished_metric_;
 
   DISALLOW_COPY_AND_ASSIGN(FirstWebContentsProfiler);
 };
 
 #endif  // CHROME_BROWSER_METRICS_FIRST_WEB_CONTENTS_PROFILER_H_