PageLoadMetricsObservers observe individual page loads

components/page_load_metrics/browser/page_load_metrics_observer.h

 // 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 COMPONENTS_PAGE_LOAD_METRICS_BROWSER_PAGE_LOAD_METRICS_OBSERVER_H_
 #define COMPONENTS_PAGE_LOAD_METRICS_BROWSER_PAGE_LOAD_METRICS_OBSERVER_H_
 
+#include "base/macros.h"
 #include "components/page_load_metrics/common/page_load_timing.h"
 #include "content/public/browser/navigation_handle.h"
 
 namespace page_load_metrics {
 
 struct PageLoadExtraInfo {
   PageLoadExtraInfo(const base::TimeDelta& first_background_time,
                     const base::TimeDelta& first_foreground_time,
-                    bool started_in_foreground);
+                    bool started_in_foreground,
+                    bool has_commit);
 
   // Returns the time to first background if the page load started in the
   // foreground. If the page has not been backgrounded, or the page started in
   // the background, this will be base::TimeDelta().
   const base::TimeDelta first_background_time;
 
   // Returns the time to first foreground if the page load started in the
   // background. If the page has not been foregrounded, or the page started in
   // the foreground, this will be base::TimeDelta().
   const base::TimeDelta first_foreground_time;
 
   // True if the page load started in the foreground.
   const bool started_in_foreground;
+
+  // True if the page load committed and received its first bytes of data.
+  const bool has_commit;
 };
 
-// Interface for PageLoadMetrics observers. Note that it might be possible for
-// OnCommit to be fired without a subsequent OnComplete (i.e. if an error
-// occurs or we don't have any metrics to log). PageLoadMetricsObservers are
-// required to stop observing (call PageLoadMetricsObservable::RemoveObserver)
-// some time before the OnPageLoadMetricsGoingAway trigger finishes. If this
-// class is destroyed before the PageLoadMetricsObservable, it should call
-// RemoveObserver in its destructor.
+// Interface for PageLoadMetrics observers. All instances of this class are
+// owned by the PageLoadTracker tracking a page load. They will be deleted after
+// calling OnComplete.
 class PageLoadMetricsObserver {
  public:
   virtual ~PageLoadMetricsObserver() {}
 
+  // The page load started, with the given navigation handle.
+  virtual void OnStart(content::NavigationHandle* navigation_handle) {}
+
   // OnRedirect is triggered when a page load redirects to another URL.
   // The navigation handle holds relevant data for the navigation, but will
-  // be destroyed soon after this call. Don't hold a reference to it.
+  // be destroyed soon after this call. Don't hold a reference to it. This can
+  // be called multiple times.
   virtual void OnRedirect(content::NavigationHandle* navigation_handle) {}
 
   // OnCommit is triggered when a page load commits, i.e. when we receive the
   // first data for the request. The navigation handle holds relevant data for
   // the navigation, but will be destroyed soon after this call. Don't hold a
   // reference to it.
   virtual void OnCommit(content::NavigationHandle* navigation_handle) {}
 
   // OnComplete is triggered when we are ready to record metrics for this page
-  // load. This will happen some time after commit, and will be triggered as
-  // long as we've received some data about the page load. The
-  // PageLoadTiming struct contains timing data and the PageLoadExtraInfo struct
-  // contains other useful information about the tab backgrounding/foregrounding
-  // over the course of the page load.
+  // load. This will happen some time after commit. The PageLoadTiming struct
+  // contains timing data and the PageLoadExtraInfo struct contains other useful
+  // data collected over the course of the page load. If the load did not
+  // receive any timing information, |timing.IsEmpty()| will be true.
+  // After this call, the object will be deleted.
   virtual void OnComplete(const PageLoadTiming& timing,
                           const PageLoadExtraInfo& extra_info) {}
-
-  // This is called when the WebContents we are observing is tearing down. No
-  // further callbacks will be triggered.
-  virtual void OnPageLoadMetricsGoingAway() {}
-};
-
-// Class which handles notifying observers when loads commit and complete. It
-// must call OnPageLoadMetricsGoingAway in the destructor.
-class PageLoadMetricsObservable {
- public:
-  virtual ~PageLoadMetricsObservable() {}
-  virtual void AddObserver(PageLoadMetricsObserver* observer) = 0;
-  virtual void RemoveObserver(PageLoadMetricsObserver* observer) = 0;
 };
 
 }  // namespace page_load_metrics
 
 #endif  // COMPONENTS_PAGE_LOAD_METRICS_BROWSER_PAGE_LOAD_METRICS_OBSERVER_H_