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..86cfcd2ef66ce65d0c197624aec5eba6d8cf26e7 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, 2016/05/18 15:21:50]

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?

+
   // 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) {}
+
+  // OnUserInteraction is triggered when a new user input is passed in to
+  // web_contents

[tdresser, 2016/05/17 13:24:53]

nit:missing period.

[tdresser, 2016/05/17 13:24:53]

It worries me a bit that these comments don't make it clear what kinds of input
are being monitored.

For example, most touch based games will _never_ trigger this. If touch events
are preventDefaulted, they won't result in a user interaction.

See rbyers.net/paint.html for an example of a page that you can interact with
(drawing with touch), without causing this to register at all.

[Bryan McQuade, 2016/05/18 15:21:50]

yeah, i agree - it seems the WCO hook we are overriding to get this signal isn't
necessarily well understood or well supported, which is worrying. tim, is there
a better canonical source of input events that we should be wiring through
WebContentsObservers to replace the hook we are using currently? I'd like to
make sure we're using a data source that input team feels is giving good data.

+  virtual void OnUserInteraction(blink::WebInputEvent::Type type) {}
 };
 
 }  // namespace page_load_metrics