[Downloads] Remove RDH from DownloadUrlParameters.

A ResourceDispatcherHost* doesn't need to be passed in
DownloadUrlParameters since there's only one instance.

BUG=7648

Review URL: https://chromiumcodereview.appspot.com/16875007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@207710 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/content/browser/download/download_manager_impl.cc b/content/browser/download/download_manager_impl.cc
index f7a8b2ee..6e0930a 100644
--- a/content/browser/download/download_manager_impl.cc
+++ b/content/browser/download/download_manager_impl.cc
@@ -124,7 +124,7 @@
   save_info->prompt_for_save_location = params->prompt();
   save_info->file_stream = params->GetFileStream();
 
-  params->resource_dispatcher_host()->BeginDownload(
+  ResourceDispatcherHost::Get()->BeginDownload(
       request.Pass(),
       params->content_initiated(),
       params->resource_context(),