Log First User Interaction in Page Load Metrics

content/browser/renderer_host/render_widget_host_impl.h

Index: content/browser/renderer_host/render_widget_host_impl.h
diff --git a/content/browser/renderer_host/render_widget_host_impl.h b/content/browser/renderer_host/render_widget_host_impl.h
index 674e463ce8a3e35e721d5f0bf2ea16067304c01b..884f349c963ec3782ff573bfdc9ec1a2bec1450d 100644
--- a/content/browser/renderer_host/render_widget_host_impl.h
+++ b/content/browser/renderer_host/render_widget_host_impl.h
@@ -169,6 +169,10 @@ class CONTENT_EXPORT RenderWidgetHostImpl : public RenderWidgetHost,
       const KeyPressEventCallback& callback) override;
   void AddMouseEventCallback(const MouseEventCallback& callback) override;
   void RemoveMouseEventCallback(const MouseEventCallback& callback) override;
+  void AddInputEventObserver(
+      RenderWidgetHost::InputEventObserver* observer) override;
+  void RemoveInputEventObserver(
+      RenderWidgetHost::InputEventObserver* observer) override;
   void GetWebScreenInfo(blink::WebScreenInfo* result) override;
   bool GetScreenColorProfile(std::vector<char>* color_profile) override;
   void HandleCompositorProto(const std::vector<uint8_t>& proto) override;
@@ -702,6 +706,10 @@ class CONTENT_EXPORT RenderWidgetHostImpl : public RenderWidgetHost,
   // Mouse event callbacks.
   std::vector<MouseEventCallback> mouse_event_callbacks_;
 
+  // Input event callbacks.
+  base::ObserverList<RenderWidgetHost::InputEventObserver>
+      input_event_observers_;
+
   // If true, then we should repaint when restoring even if we have a
   // backingstore.  This flag is set to true if we receive a paint message
   // while is_hidden_ to true.  Even though we tell the render widget to hide