Bug fix: Use the last hidden time for purge + suspend

content/public/browser/web_contents.h

Index: content/public/browser/web_contents.h
diff --git a/content/public/browser/web_contents.h b/content/public/browser/web_contents.h
index 697ea3aee21d2fd89ce3a7252ce7c73c34c5797a..7eaa25270321d1547375d50b2941abfcbeccec81 100644
--- a/content/public/browser/web_contents.h
+++ b/content/public/browser/web_contents.h
@@ -402,6 +402,9 @@ class WebContents : public PageNavigator,
   virtual base::TimeTicks GetLastActiveTime() const = 0;
   virtual void SetLastActiveTime(base::TimeTicks last_active_time) = 0;
 
+  // Get the last time that the WebContents was made hidden.
+  virtual base::TimeTicks GetLastHiddenTime() const = 0;
+
   // Invoked when the WebContents becomes shown/hidden.
   virtual void WasShown() = 0;
   virtual void WasHidden() = 0;