Remove Futures class, move methods to Future.

utils/apidoc/apidoc.dart

Index: utils/apidoc/apidoc.dart
diff --git a/utils/apidoc/apidoc.dart b/utils/apidoc/apidoc.dart
index 0fd572c8bf46560b2c988b5225363265f76087f8..c2c119c9558f930fc6922e3389735e13c3169a53 100644
--- a/utils/apidoc/apidoc.dart
+++ b/utils/apidoc/apidoc.dart
@@ -146,12 +146,12 @@ void main() {
     apidoc.includeApi = true;
     apidoc.includedLibraries = includedLibraries;
 
-    Futures.wait([copiedStatic, copiedApiDocStatic]).then((_) {
+    Future.wait([copiedStatic, copiedApiDocStatic]).then((_) {
       apidoc.documentLibraries(apidocLibraries, libPath, pkgPath);
 
       final compiled = doc.compileScript(mode, outputDir, libPath);
 
-      Futures.wait([compiled, copiedStatic, copiedApiDocStatic]).then((_) {
+      Future.wait([compiled, copiedStatic, copiedApiDocStatic]).then((_) {
         apidoc.cleanup();
       });
     });