Adding previews information to PLM UKM

chrome/browser/page_load_metrics/metrics_web_contents_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 CHROME_BROWSER_PAGE_LOAD_METRICS_METRICS_WEB_CONTENTS_OBSERVER_H_
 #define CHROME_BROWSER_PAGE_LOAD_METRICS_METRICS_WEB_CONTENTS_OBSERVER_H_
 
 #include <map>
 #include <memory>
 #include <vector>
@@ skipping 120 matching lines @@
 
   // Register / unregister TestingObservers. Should only be called from tests.
   void AddTestingObserver(TestingObserver* observer);
   void RemoveTestingObserver(TestingObserver* observer);
 
   // public only for testing
   void OnTimingUpdated(content::RenderFrameHost* render_frame_host,
                        const mojom::PageLoadTiming& timing,
                        const mojom::PageLoadMetadata& metadata);
 
+  // Informs the observers of the currently committed load that the event
+  // corresponding to |event_key| has occurred. This should not be called within
+  // WebContentsObserver::DidFinishNavigation methods.
+  void BroadcastEventToObservers(const void* const event_key);

[Bryan McQuade, 2017/07/12 21:10:03]

let's add to the comment that this API is subject to change and may be removed
in the future - my hope is to get rid of this in favor for looking up observer
by type, but that'll take a bit more time.

[RyanSturm, 2017/07/12 21:27:27]

Done.

+
  private:
   friend class content::WebContentsUserData<MetricsWebContentsObserver>;
 
   // page_load_metrics::mojom::PageLoadMetrics implementation.
   void UpdateTiming(mojom::PageLoadTimingPtr timing,
                     mojom::PageLoadMetadataPtr metadata) override;
 
   void HandleFailedNavigationForTrackedLoad(
       content::NavigationHandle* navigation_handle,
       std::unique_ptr<PageLoadTracker> tracker);
@@ skipping 64 matching lines @@
   base::ObserverList<TestingObserver> testing_observers_;
   content::WebContentsFrameBindingSet<mojom::PageLoadMetrics>
       page_load_metrics_binding_;
 
   DISALLOW_COPY_AND_ASSIGN(MetricsWebContentsObserver);
 };
 
 }  // namespace page_load_metrics
 
 #endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_METRICS_WEB_CONTENTS_OBSERVER_H_