Abandon startup profiling for first WebContents when it gets hidden or navigated to a different ...

chrome/browser/metrics/first_web_contents_profiler.h

Index: chrome/browser/metrics/first_web_contents_profiler.h
diff --git a/chrome/browser/metrics/first_web_contents_profiler.h b/chrome/browser/metrics/first_web_contents_profiler.h
index 23a51a288af72075a16d9e632e7e87c52de062e1..9d2539386aa5b45e30584a8f313b6a94e5b399d6 100644
--- a/chrome/browser/metrics/first_web_contents_profiler.h
+++ b/chrome/browser/metrics/first_web_contents_profiler.h
@@ -34,24 +34,49 @@ class FirstWebContentsProfiler : public content::WebContentsObserver {
       Delegate* delegate);
 
  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,
+    // Must stay last.
+    COUNT

[rkaplow, 2015/10/20 20:08:30]

usually I see this as something like ENUM_MAX which is a bit more obvious but
not a big deal

[gab, 2015/10/20 20:16:21]

Done.

+  };
+
   FirstWebContentsProfiler(content::WebContents* web_contents,
                            Delegate* delegate);
 
   // 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.
-  void FinishedCollectingMetrics();
+  // metrics. Logs |finish_reason| to UMA.
+  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_;