overscroll: Take a screenshot at more appropriate times.

content/browser/web_contents/navigation_controller_impl.h

Index: content/browser/web_contents/navigation_controller_impl.h
diff --git a/content/browser/web_contents/navigation_controller_impl.h b/content/browser/web_contents/navigation_controller_impl.h
index 275ba2a4262a5dc5932e2719df600751aad47b69..dbc9ed8b3cbc66edde63144ad02c7ac226312faa 100644
--- a/content/browser/web_contents/navigation_controller_impl.h
+++ b/content/browser/web_contents/navigation_controller_impl.h
@@ -199,6 +199,9 @@ class CONTENT_EXPORT NavigationControllerImpl
   void SetGetTimestampCallbackForTest(
       const base::Callback<base::Time()>& get_timestamp_callback);
 
+  // Takes a screenshot of the page at the current state.
+  void TakeScreenshot();
+
  private:
   friend class RestoreHelper;
   friend class WebContentsImpl;  // For invoking OnReservedPageIDRange.
@@ -312,9 +315,6 @@ class CONTENT_EXPORT NavigationControllerImpl
   // specified |offset|.  The index returned is not guaranteed to be valid.
   int GetIndexForOffset(int offset) const;
 
-  // Takes a screenshot of the page at the current state.
-  void TakeScreenshot();
-
   // The callback invoked when taking the screenshot of the page is complete.
   // This sets the screenshot on the navigation entry.
   void OnScreenshotTaken(int unique_id,