GTK: Compile fix for Natty in history menu code

chrome/browser/ui/gtk/global_history_menu.cc

Index: chrome/browser/ui/gtk/global_history_menu.cc
diff --git a/chrome/browser/ui/gtk/global_history_menu.cc b/chrome/browser/ui/gtk/global_history_menu.cc
index 83c861c3d3cffaa69083d6032abd10e23b405def..3df4b58523376c1b7952a524b251a7f3f7b2b299 100644
--- a/chrome/browser/ui/gtk/global_history_menu.cc
+++ b/chrome/browser/ui/gtk/global_history_menu.cc
@@ -222,7 +222,7 @@ void GlobalHistoryMenu::GotFaviconData(FaviconService::Handle handle,
           profile_->GetFaviconService(Profile::EXPLICIT_ACCESS), handle);
   DCHECK(item);
   item->icon_requested = false;
-  item->icon_handle = NULL;
+  item->icon_handle = static_cast<CancelableRequestProvider::Handle>(NULL);
 
   SkBitmap icon;
   if (favicon.is_valid() &&
@@ -249,7 +249,7 @@ void GlobalHistoryMenu::CancelFaviconRequest(HistoryItem* item) {
         profile_->GetFaviconService(Profile::EXPLICIT_ACCESS);
     service->CancelRequest(item->icon_handle);
     item->icon_requested = false;
-    item->icon_handle = NULL;
+    item->icon_handle = static_cast<CancelableRequestProvider::Handle>(NULL);
   }
 }