Factor out dependncy on download throttling from core download code.

chrome/browser/ui/tab_contents/tab_contents_wrapper.h

Index: chrome/browser/ui/tab_contents/tab_contents_wrapper.h
===================================================================
--- chrome/browser/ui/tab_contents/tab_contents_wrapper.h	(revision 96872)
+++ chrome/browser/ui/tab_contents/tab_contents_wrapper.h	(working copy)
@@ -32,6 +32,7 @@
 class AutomationTabHelper;
 class BlockedContentTabHelper;
 class BookmarkTabHelper;
+class DownloadRequestLimiterObserver;
 class Extension;
 class ExtensionTabHelper;
 class ExtensionWebNavigationTabObserver;
@@ -334,6 +335,7 @@
   // (These provide no API for callers; objects that need to exist 1:1 with tabs
   // and silently do their thing live here.)
 
+  scoped_ptr<DownloadRequestLimiterObserver> download_request_limiter_observer_;
   scoped_ptr<ExternalProtocolObserver> external_protocol_observer_;
   scoped_ptr<FileSelectObserver> file_select_observer_;
   scoped_ptr<PluginObserver> plugin_observer_;