Propogate the tab foreground, background change events to data use

chrome/browser/data_use_measurement/chrome_data_use_ascriber.h

Index: chrome/browser/data_use_measurement/chrome_data_use_ascriber.h
diff --git a/chrome/browser/data_use_measurement/chrome_data_use_ascriber.h b/chrome/browser/data_use_measurement/chrome_data_use_ascriber.h
index c50efd730825d1ba5e67cb09119dfe4d8306c54f..a05d8a8b57a2dec762ce3b0f4e5cadc14d83c61e 100644
--- a/chrome/browser/data_use_measurement/chrome_data_use_ascriber.h
+++ b/chrome/browser/data_use_measurement/chrome_data_use_ascriber.h
@@ -91,6 +91,16 @@ class ChromeDataUseAscriber : public DataUseAscriber {
       bool is_same_page_navigation,
       void* navigation_handle);
 
+  // Called every time the WebContents changes visibility.
+  void WasShownOrHidden(int main_render_process_id,
+                        int main_render_frame_id,
+                        bool visible);
+
+  // Called whenever one of the render frames of a WebContents is swapped.
+  void RenderFrameHostChanged(int old_render_process_id,
+                              int old_render_frame_id,
+                              int new_render_process_id,
+                              int new_render_frame_id);
 
  private:
   friend class ChromeDataUseAscriberTest;
@@ -156,6 +166,9 @@ class ChromeDataUseAscriber : public DataUseAscriber {
                      GlobalRequestIDHash>
       pending_navigation_data_use_map_;
 
+  // Contains the mainframe IDs that are currently visible.
+  base::hash_set<RenderFrameHostID> visible_main_render_frames_;
+
   DISALLOW_COPY_AND_ASSIGN(ChromeDataUseAscriber);
 };