Prototype for improved and generalized immediate event logging.

components/page_load_metrics/browser/page_load_metrics_observer.h

Index: components/page_load_metrics/browser/page_load_metrics_observer.h
diff --git a/components/page_load_metrics/browser/page_load_metrics_observer.h b/components/page_load_metrics/browser/page_load_metrics_observer.h
index 6a2a2c6100c239b2389fa5f801c69837b4e84eca..d29349e4a044cf989ad3052f7d892face781b685 100644
--- a/components/page_load_metrics/browser/page_load_metrics_observer.h
+++ b/components/page_load_metrics/browser/page_load_metrics_observer.h
@@ -144,6 +144,37 @@ class PageLoadMetricsObserver {
                           const PageLoadExtraInfo& extra_info) {}
 };
 
+class PageLoadMetricsEventObserver {
+ public:
+  void HandleTimingUpdate(const PageLoadTiming& timing,
+                          const PageLoadExtraInfo& extra_info);
+
+ protected:
+  virtual void OnDomContentLoadedEventStart(
+      const PageLoadTiming& timing,
+      const PageLoadExtraInfo& extra_info) {}
+  virtual void OnLoadEventStart(const PageLoadTiming& timing,
+                                const PageLoadExtraInfo& extra_info) {}
+  virtual void OnFirstLayout(const PageLoadTiming& timing,
+                             const PageLoadExtraInfo& extra_info) {}
+  virtual void OnFirstPaint(const PageLoadTiming& timing,
+                            const PageLoadExtraInfo& extra_info) {}
+  virtual void OnFirstTextPaint(const PageLoadTiming& timing,
+                                const PageLoadExtraInfo& extra_info) {}
+  virtual void OnFirstImagePaint(const PageLoadTiming& timing,
+                                 const PageLoadExtraInfo& extra_info) {}
+  virtual void OnFirstContentfulPaint(const PageLoadTiming& timing,
+                                      const PageLoadExtraInfo& extra_info) {}
+  virtual void OnParseStart(const PageLoadTiming& timing,
+                            const PageLoadExtraInfo& extra_info) {}
+  virtual void OnParseStop(const PageLoadTiming& timing,
+                           const PageLoadExtraInfo& extra_info) {}
+
+ private:
+  // The last timing provided to OnTimingUpdate.
+  PageLoadTiming last_timing_;
+};
+
 }  // namespace page_load_metrics
 
 #endif  // COMPONENTS_PAGE_LOAD_METRICS_BROWSER_PAGE_LOAD_METRICS_OBSERVER_H_