Implement a site engagement score based on time-on-site.

chrome/browser/engagement/site_engagement_helper.h

Index: chrome/browser/engagement/site_engagement_helper.h
diff --git a/chrome/browser/engagement/site_engagement_helper.h b/chrome/browser/engagement/site_engagement_helper.h
index c3883d5cf41a1363e67469f1c0e0bcf2d7635844..af059d431b24d98915c81add6e339156697d6519 100644
--- a/chrome/browser/engagement/site_engagement_helper.h
+++ b/chrome/browser/engagement/site_engagement_helper.h
@@ -6,6 +6,8 @@
 #define CHROME_BROWSER_ENGAGEMENT_SITE_ENGAGEMENT_HELPER_H_
 
 #include "base/macros.h"
+#include "base/timer/timer.h"
+#include "content/public/browser/render_view_host.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
 
@@ -16,21 +18,87 @@ class WebContents;
 class GURL;
 
 // Per-WebContents class to handle updating the site engagement scores for
-// origins as the user navigates.
+// origins.
 class SiteEngagementHelper
     : public content::WebContentsObserver,
       public content::WebContentsUserData<SiteEngagementHelper> {
  public:
   ~SiteEngagementHelper() override;
 
+  static void SetSecondsBetweenUserInputCheck(double seconds);
+
  private:
+  // Class to encapsulate the user input listening.
+  //
+  // Time on site is recorded by detecting any user input (mouse or keypress)
+  // per some discrete time unit. If there is user input, then record a positive
+  // site engagement.
+  //
+  // When input is detected, SiteEngagementHelper::RecordUserInput is called,
+  // and the input detection callbacks are paused for
+  // g_seconds_between_user_input_check. This ensures that there is minimal
+  // overhead in input listening, and that input over an extended length of time
+  // is required to continually increase the engagement score.
+  class InputTracker {
+   public:
+    explicit InputTracker(SiteEngagementHelper* helper);
+    ~InputTracker();
+
+    // Callback to handle key press events from the RenderViewHost.
+    bool HandleKeyPressEvent(const content::NativeWebKeyboardEvent& event);
+
+    // Callback to handle mouse events from the RenderViewHost.
+    bool HandleMouseEvent(const blink::WebMouseEvent& event);
+
+    // Register callbacks to listen for user input.
+    void StartTracking(content::RenderViewHost* host);
+
+    // Pause listening for user input, restarting listening after
+    // g_seconds_between_user_input_check seconds.
+    void PauseTracking(content::RenderViewHost* host);
+
+    // Restart listening for user input.
+    void ResumeTracking();
+
+    // Stop listening for user input.
+    void StopTracking(content::RenderViewHost* host);
+
+    // Set the timer object for testing purposes.
+    void SetTimerForTesting(scoped_ptr<base::Timer> timer);
+
+    bool callbacks_added() { return callbacks_added_; }
+
+   private:
+    SiteEngagementHelper* helper_;
+    scoped_ptr<base::Timer> pause_timer_;
+    content::RenderWidgetHost::KeyPressEventCallback key_press_event_callback_;
+    content::RenderWidgetHost::MouseEventCallback mouse_event_callback_;
+    bool callbacks_added_;
+  };
+
   explicit SiteEngagementHelper(content::WebContents* web_contents);
   friend class content::WebContentsUserData<SiteEngagementHelper>;
+  friend class SiteEngagementServiceBrowserTest;
+
+  // Ask the SiteEngagementService to record engagement via user input at the
+  // current contents location.
+  void RecordUserInput();
+
+  bool ShouldRecordEngagement();
 
   // content::WebContentsObserver overrides.
-  void DidStartNavigationToPendingEntry(
-      const GURL& url,
-      content::NavigationController::ReloadType reload_type) override;
+  void DidNavigateMainFrame(
+      const content::LoadCommittedDetails& details,
+      const content::FrameNavigateParams& params) override;
+
+  void RenderViewHostChanged(content::RenderViewHost* old_host,
+                             content::RenderViewHost* new_host) override;
+
+  void WasShown() override;
+  void WasHidden() override;
+
+  InputTracker input_tracker_;
+  bool record_engagement_;
 
   DISALLOW_COPY_AND_ASSIGN(SiteEngagementHelper);
 };