Use filter context to track stats better in SDCH filtering

net/url_request/url_request_http_job.cc

Index: net/url_request/url_request_http_job.cc
===================================================================
--- net/url_request/url_request_http_job.cc	(revision 11636)
+++ net/url_request/url_request_http_job.cc	(working copy)
@@ -204,10 +204,7 @@
   }
 
   if (!encoding_types->empty()) {
-    std::string mime_type;
-    GetMimeType(&mime_type);
-    // TODO(jar): Need to change this call to use the FilterContext interfaces.
-    Filter::FixupEncodingTypes(IsSdchResponse(), mime_type, encoding_types);
+    Filter::FixupEncodingTypes(*this, encoding_types);
   }
   return !encoding_types->empty();
 }