Refactor ownership model for FirstWebContentsProfiler.

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 "base/memory/scoped_ptr.h"
 #include "base/metrics/histogram.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:
-  class Delegate {
-   public:
-    // Called by the FirstWebContentsProfiler when it is finished collecting
-    // metrics. The delegate should take this opportunity to destroy the
-    // FirstWebContentsProfiler.
-    virtual void ProfilerFinishedCollectingMetrics() = 0;
-  };
-
   // Creates a profiler for the active web contents. If there are multiple
-  // browsers, the first one is chosen. If there are no browsers, returns
-  // nullptr.
-  static scoped_ptr<FirstWebContentsProfiler> CreateProfilerForFirstWebContents(
-      Delegate* delegate);
+  // browsers, the first one is chosen. The resulting FirstWebContentsProfiler
+  // owns itself.
+  static void Start();
 
  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_NAVIGATION = 4,
     ENUM_MAX
   };
 
-  FirstWebContentsProfiler(content::WebContents* web_contents,
-                           Delegate* delegate);
+  explicit FirstWebContentsProfiler(content::WebContents* web_contents);
+  ~FirstWebContentsProfiler() override = default;
 
   // content::WebContentsObserver:
   void DidFirstVisuallyNonEmptyPaint() override;
   void DocumentOnLoadCompletedInMainFrame() override;
   void NavigationEntryCommitted(
       const content::LoadCommittedDetails& load_details) override;
   void WasHidden() override;
   void WebContentsDestroyed() override;
 
   // Whether this instance has finished collecting all of its metrics.
   bool IsFinishedCollectingMetrics();
 
-  // Informs the delegate that this instance has finished collecting all of its
-  // metrics. Logs |finish_reason| to UMA.
+  // Logs |finish_reason| to UMA and deletes this FirstWebContentsProfiler.
   void FinishedCollectingMetrics(FinishReason finish_reason);
 
   // Initialize histograms for unresponsiveness metrics.
   void InitHistograms();
 
   // Becomes true on the first invocation of NavigationEntryCommitted() for the
   // main frame. Any follow-up navigation to a different page will result in
   // aborting first WebContents profiling.
   bool initial_entry_committed_;
 
   // Whether an attempt was made to collect the "NonEmptyPaint" metric.
   bool collected_paint_metric_;
 
   // Whether an attempt was made to collect the "MainFrameLoad" metric.
   bool collected_load_metric_;
 
-  // |delegate_| owns |this|.
-  Delegate* delegate_;
-
   // Histogram that keeps track of response times for the watched thread.
   base::HistogramBase* responsiveness_histogram_;
 
   // Histogram that keeps track of response times for the watched thread.
   base::HistogramBase* responsiveness_1sec_histogram_;
 
   // Histogram that keeps track of response times for the watched thread.
   base::HistogramBase* responsiveness_10sec_histogram_;
 
   // Histogram that keeps track of response times for the watched thread.
   base::HistogramBase* unresponsiveness_histogram_;
 
   // Histogram that keeps track of response times for the watched thread.
   base::HistogramBase* unresponsiveness_1sec_histogram_;
 
   // Histogram that keeps track of response times for the watched thread.
   base::HistogramBase* unresponsiveness_10sec_histogram_;
 
   DISALLOW_COPY_AND_ASSIGN(FirstWebContentsProfiler);
 };
 
 #endif  // CHROME_BROWSER_METRICS_FIRST_WEB_CONTENTS_PROFILER_H_