Bug 1518863: Part 0 - Minor extension protocol handler cleanup. r=aswan

These are trivial issues that I'd rather keep out of the main patch.

Differential Revision: https://phabricator.services.mozilla.com/D21444

--HG--
extra : rebase_source : c607248dd2d44673b84f4bc99464c3f15a639add

netwerk/protocol/res/ExtensionProtocolHandler.cpp

@@ -423,18 +423,16 @@ Result<Ok, nsresult> ExtensionProtocolHandler::SubstituteRemoteChannel(
 nsresult ExtensionProtocolHandler::SubstituteChannel(nsIURI* aURI,
                                                      nsILoadInfo* aLoadInfo,
                                                      nsIChannel** result) {
-  nsresult rv;
-  nsCOMPtr<nsIURL> url = do_QueryInterface(aURI, &rv);
-  NS_ENSURE_SUCCESS(rv, rv);
-
   if (mUseRemoteFileChannels) {
     MOZ_TRY(SubstituteRemoteChannel(aURI, aLoadInfo, result));
   }
 
-  nsAutoCString ext;
+  nsresult rv;
-  rv = url->GetFileExtension(ext);
+  nsCOMPtr<nsIURL> url = do_QueryInterface(aURI, &rv);
-  NS_ENSURE_SUCCESS(rv, rv);
+  MOZ_TRY(rv);
 
+  nsAutoCString ext;
+  MOZ_TRY(url->GetFileExtension(ext));
   if (!ext.LowerCaseEqualsLiteral("css")) {
     return NS_OK;
   }