Reapply 'Add reduce to Collection.'

runtime/lib/byte_array.dart

Index: runtime/lib/byte_array.dart
diff --git a/runtime/lib/byte_array.dart b/runtime/lib/byte_array.dart
index 9db082aa2a5c9d628f169288fde670bddec647f2..60d0ecf2e661f92dad9e9523165e101be68b9503 100644
--- a/runtime/lib/byte_array.dart
+++ b/runtime/lib/byte_array.dart
@@ -812,6 +812,11 @@ abstract class _ByteArrayBase {
                            f);
   }
 
+  Dynamic reduce(Dynamic initialValue,
+                 Dynamic combine(Dynamic initialValue, element)) {
+    return Collections.reduce(this, initialValue, combine);
+  }
+
   Collection filter(bool f(element)) {
     return Collections.filter(this, new GrowableObjectArray(), f);
   }
@@ -2286,6 +2291,11 @@ class _ByteArrayViewBase {
                            f);
   }
 
+  Dynamic reduce(Dynamic initialValue,
+                 Dynamic combine(Dynamic initialValue, element)) {
+    return Collections.reduce(this, initialValue, combine);
+  }
+
   Collection filter(bool f(element)) {
     return Collections.filter(this, new GrowableObjectArray(), f);
   }