Remove Futures class, move methods to Future.

utils/pub/curl_client.dart

Index: utils/pub/curl_client.dart
diff --git a/utils/pub/curl_client.dart b/utils/pub/curl_client.dart
index cd74df95f7c91e80af5846c84a41839b5fb5020c..168178888e93b6ebe9919b744c52eb43c40cb7c1 100644
--- a/utils/pub/curl_client.dart
+++ b/utils/pub/curl_client.dart
@@ -136,7 +136,7 @@ class CurlClient extends http.BaseClient {
     // prints the headers to stdout instead of the body. We want to wait until
     // all the headers are received to read them from the header file.
     if (!expectBody) {
-      return Futures.wait([
+      return Future.wait([
         consumeInputStream(process.stdout),
         completer.future
       ]);