Replace PruneAllButActive with PruneAllButVisible.

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 5e50d109c074ee7de230791218a22ca4c2de7fc7..92ee8aff42b931ea10449514535b4031fd6761e1 100644
--- a/content/browser/web_contents/navigation_controller_impl.h
+++ b/content/browser/web_contents/navigation_controller_impl.h
@@ -89,7 +89,8 @@ class CONTENT_EXPORT NavigationControllerImpl
       const NavigationController& source) OVERRIDE;
   virtual void CopyStateFromAndPrune(
       NavigationController* source) OVERRIDE;
-  virtual void PruneAllButActive() OVERRIDE;
+  virtual bool CanPruneAllButVisible() OVERRIDE;
+  virtual void PruneAllButVisible() OVERRIDE;
   virtual void ClearAllScreenshots() OVERRIDE;
 
   // The session storage namespace that all child RenderViews belonging to
@@ -293,10 +294,11 @@ class CONTENT_EXPORT NavigationControllerImpl
   // preparation to add another.
   void PruneOldestEntryIfFull();
 
-  // Removes all the entries except the active entry. If there is a new pending
-  // navigation it is preserved. In contrast to PruneAllButActive() this does
-  // not update the session history of the RenderView.
-  void PruneAllButActiveInternal();
+  // Removes all entries except the last committed entry.  If there is a new
+  // pending navigation it is preserved. In contrast to PruneAllButVisible()
+  // this does not update the session history of the RenderView.  Callers
+  // must ensure that |CanPruneAllButVisible| returns true before calling this.
+  void PruneAllButVisibleInternal();
 
   // Returns true if the navigation is redirect.
   bool IsRedirect(const ViewHostMsg_FrameNavigate_Params& params);