Log First User Interaction in Page Load Metrics

content/public/browser/render_widget_host.h

Index: content/public/browser/render_widget_host.h
diff --git a/content/public/browser/render_widget_host.h b/content/public/browser/render_widget_host.h
index 4fb43f99f835689d1c03c00a86ee59773a24f11f..0ea285ecc874ff9b9cfaa688e0b3364f41e57b5d 100644
--- a/content/public/browser/render_widget_host.h
+++ b/content/public/browser/render_widget_host.h
@@ -244,6 +244,17 @@ class CONTENT_EXPORT RenderWidgetHost : public IPC::Sender {
   virtual void AddMouseEventCallback(const MouseEventCallback& callback) = 0;
   virtual void RemoveMouseEventCallback(const MouseEventCallback& callback) = 0;
 
+  // Add/remove a observer that can handle all kinds of input events.
+  class InputEventObserver {
+   public:
+    virtual ~InputEventObserver() {}
+
+    virtual bool OnInputEvent(const blink::WebInputEvent&) = 0;
+  };
+
+  virtual void AddInputEventObserver(InputEventObserver* observer) = 0;
+  virtual void RemoveInputEventObserver(InputEventObserver* observer) = 0;
+
   // Get the screen info corresponding to this render widget.
   virtual void GetWebScreenInfo(blink::WebScreenInfo* result) = 0;
   // Get the color profile corresponding to this render widget.