Remove dead code

chrome/browser/history/top_sites.h

Index: chrome/browser/history/top_sites.h
diff --git a/chrome/browser/history/top_sites.h b/chrome/browser/history/top_sites.h
index b0bdcb963c41e72bade06913d11ad77a93112840..47ed7de8cfe4b78d75d2d05e6d687adafbeb744e 100644
--- a/chrome/browser/history/top_sites.h
+++ b/chrome/browser/history/top_sites.h
@@ -9,7 +9,6 @@
 #include "base/callback.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/ref_counted.h"
-#include "chrome/browser/common/cancelable_request.h"
 #include "chrome/browser/history/history_service.h"
 #include "chrome/browser/history/history_types.h"
 #include "components/history/core/common/thumbnail_score.h"
@@ -121,9 +120,9 @@ class TopSites
   virtual void Shutdown() = 0;
 
   // Query history service for the list of available thumbnails. Returns the
-  // handle for the request, or NULL if a request could not be made.
-  // Public only for testing purposes.
-  virtual CancelableRequestProvider::Handle StartQueryForMostVisited() = 0;
+  // task id for the request, or |base::CancelableTaskTracker::kBadTaskId| if a
+  // request could not be made. Public only for testing purposes.
+  virtual base::CancelableTaskTracker::TaskId StartQueryForMostVisited() = 0;
 
   // Returns true if the given URL is known to the top sites service.
   // This function also returns false if TopSites isn't loaded yet.