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

content/browser/web_contents/web_contents_impl.h

Index: content/browser/web_contents/web_contents_impl.h
diff --git a/content/browser/web_contents/web_contents_impl.h b/content/browser/web_contents/web_contents_impl.h
index 3afb1aab039d99d206c9b33af0d666dbd9d6c669..000a9316e71c54b5e5392441ff6a4041ccc64586 100644
--- a/content/browser/web_contents/web_contents_impl.h
+++ b/content/browser/web_contents/web_contents_impl.h
@@ -327,6 +327,7 @@ class CONTENT_EXPORT WebContentsImpl
   void NotifyNavigationStateChanged(InvalidateTypes changed_flags) override;
   base::TimeTicks GetLastActiveTime() const override;
   void SetLastActiveTime(base::TimeTicks last_active_time) override;
+  base::TimeTicks GetLastHiddenTime() const override;
   void WasShown() override;
   void WasHidden() override;
   bool NeedToFireBeforeUnload() override;
@@ -1270,6 +1271,10 @@ class CONTENT_EXPORT WebContentsImpl
   // the WebContents creation time.
   base::TimeTicks last_active_time_;
 
+  // The time that this WebContents was last made hidden. The initial value is
+  // zero.
+  base::TimeTicks last_hidden_time_;
+
   // See description above setter.
   bool closed_by_user_gesture_;