Log First User Interaction in Page Load Metrics

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 b5e951f5cba965244f62b00df04e25c7acaaa9b6..45bd4ae7df0464c077e1dd499ddc16419f4c3a22 100644
--- a/components/page_load_metrics/browser/page_load_metrics_observer.h
+++ b/components/page_load_metrics/browser/page_load_metrics_observer.h
@@ -8,6 +8,7 @@
 #include "base/macros.h"
 #include "components/page_load_metrics/common/page_load_timing.h"
 #include "content/public/browser/navigation_handle.h"
+#include "third_party/WebKit/public/web/WebInputEvent.h"
 #include "url/gurl.h"
 
 namespace page_load_metrics {
@@ -51,6 +52,7 @@ enum UserAbortType {
 struct PageLoadExtraInfo {
   PageLoadExtraInfo(base::TimeDelta first_background_time,
                     base::TimeDelta first_foreground_time,
+                    base::TimeDelta first_user_interaction_time,
                     bool started_in_foreground,
                     const GURL& committed_url,
                     base::TimeDelta time_to_commit,
@@ -67,6 +69,10 @@ struct PageLoadExtraInfo {
   // If the page has not been foregrounded this will be base::TimeDelta().
   const base::TimeDelta first_foreground_time;
 
+  // The first time that the page was given a user input since the navigation
+  // started.
+  const base::TimeDelta first_user_interaction_time;

[Bryan McQuade, 2016/05/25 20:59:23]

just copying an earlier comment i made forward since i didn't see it addressed
(sorry if i missed any comments on it):

i'm actually not sure if this is a generally useful bit of information we want
to be providing in this struct. in particular, if the first interaction happened
before anything was painted (while the screen is blank), is that likely to be
useful to most consumers?

perhaps all consumers should instead implement the OnUserInput callback to store
just the times they are interested in, and we get rid of this TimeDelta in this
struct? If we find that multiple observers are recording the same timestamp
(e.g. first interaction after contentful paint) we can then consider adding it
to this struct and refactoring at that time.

+
   // True if the page load started in the foreground.
   const bool started_in_foreground;
 
@@ -164,6 +170,10 @@ class PageLoadMetricsObserver {
                             const PageLoadExtraInfo& extra_info) {}
   virtual void OnParseStop(const PageLoadTiming& timing,
                            const PageLoadExtraInfo& extra_info) {}
+
+  // OnUserInput is triggered when a new user input is passed in to
+  // web_contents

[tdresser, 2016/05/24 14:28:38]

Missing .

+  virtual void OnUserInput(const blink::WebInputEvent& event) {}
 };
 
 }  // namespace page_load_metrics