Add some support for the code-point code-unit distinction.

sdk/lib/_internal/compiler/implementation/lib/core_patch.dart

Index: sdk/lib/_internal/compiler/implementation/lib/core_patch.dart
diff --git a/sdk/lib/_internal/compiler/implementation/lib/core_patch.dart b/sdk/lib/_internal/compiler/implementation/lib/core_patch.dart
index f75c3d7998b56307202d4083157c04b84a5ecb0f..6e33bd2fbf7d836ec3771cda12ef801fb7aba03d 100644
--- a/sdk/lib/_internal/compiler/implementation/lib/core_patch.dart
+++ b/sdk/lib/_internal/compiler/implementation/lib/core_patch.dart
@@ -169,13 +169,22 @@ patch class _ListImpl<E> {
 
 // Patch for String implementation.
 patch class _StringImpl {
-  patch factory String.fromCharCodes(List<int> charCodes) {
-    checkNull(charCodes);
-    if (!isJsArray(charCodes)) {
-      if (charCodes is !List) throw new ArgumentError(charCodes);
-      charCodes = new List.from(charCodes);
+  patch factory String.fromCharCodes(List<int> codePoints) {
+    checkNull(codePoints);
+    if (!isJsArray(codePoints)) {
+      if (codePoints is !List) throw new ArgumentError(codePoints);
+      codePoints = new List.from(codePoints);
     }
-    return Primitives.stringFromCharCodes(charCodes);
+    return Primitives.stringFromCharCodes(codePoints);
+  }
+
+  patch factory String.fromCodeUnits(List<int> codeUnits) {
+    checkNull(codeUnits);
+    if (!isJsArray(codeUnits)) {
+      if (codeUnits is !List) throw new ArgumentError(codeUnits);
+      codeUnits = new List.from(codeUnits);
+    }
+    return Primitives.stringFromCodeUnits(codeUnits);
   }
 
   patch static String join(List<String> strings, String separator) {