Fix breakage in the JavaScript compilers.

lib/compiler/implementation/lib/mock.dart

Index: lib/compiler/implementation/lib/mock.dart
diff --git a/lib/compiler/implementation/lib/mock.dart b/lib/compiler/implementation/lib/mock.dart
index 018ac150a2f7b93ac716e2c7de75859b2a8149d5..98e4e772581c3739b01be6a1c0b7a017893b260a 100644
--- a/lib/compiler/implementation/lib/mock.dart
+++ b/lib/compiler/implementation/lib/mock.dart
@@ -27,13 +27,13 @@ class StaticResolutionException implements Exception {}
 void assert(condition) {}
 
 // TODO(ahe): Not sure ByteArray belongs in the core library.
-interface ByteArray extends List default _InternalByteArray {
-  ByteArray(int length);
+interface Uint8List extends List default _InternalByteArray {
+  Uint8List(int length);
 }
 
 class _InternalByteArray {
-  factory ByteArray(int length) {
-    throw new UnsupportedOperationException("new ByteArray($length)");
+  factory Uint8List(int length) {
+    throw new UnsupportedOperationException("new Uint8List($length)");
   }
 }