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 f41085d53dc8c6bf1396636d372cabe4c21e2286..8744e32e0150fbbc0f24e51744dc595973fe3fc8 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 {
@@ -153,6 +154,11 @@ class PageLoadMetricsObserver {
   virtual void OnComplete(const PageLoadTiming& timing,
                           const PageLoadExtraInfo& extra_info) {}
 
+  // OnUserInput is triggered when a new user input is passed in to
+  // web_contents. Contains a TimeDelta from navigation start.
+  virtual void OnUserInput(const blink::WebInputEvent& event,
+                           const base::TimeDelta time_to_input) {}
+
   // The following methods are invoked at most once, when the timing for the
   // associated event first becomes available.
   virtual void OnDomContentLoadedEventStart(