Remove deprecated string features.

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

Index: sdk/lib/_internal/compiler/implementation/lib/js_string.dart
diff --git a/sdk/lib/_internal/compiler/implementation/lib/js_string.dart b/sdk/lib/_internal/compiler/implementation/lib/js_string.dart
index 6d81f320c994d8b780d01512fd824d4ff934caa5..c271e1606fea07b7d644072a6cc41ca19440167e 100644
--- a/sdk/lib/_internal/compiler/implementation/lib/js_string.dart
+++ b/sdk/lib/_internal/compiler/implementation/lib/js_string.dart
@@ -13,8 +13,6 @@ part of _interceptors;
 class JSString implements String {
   const JSString();
 
-  int charCodeAt(index) => codeUnitAt(index);
-
   int codeUnitAt(int index) {
     if (index is !num) throw new ArgumentError(index);
     if (index < 0) throw new RangeError.value(index);
@@ -71,10 +69,6 @@ class JSString implements String {
     }
   }
 
-  List<String> splitChars() {
-    return JS('=List', r'#.split("")', this);
-  }
-
   bool startsWith(String other) {
     checkString(other);
     int otherLength = other.length;
@@ -141,15 +135,7 @@ class JSString implements String {
     return JS('String', r'#.trim()', this);
   }
 
-  List<int> get charCodes  {
-    List<int> result = new List<int>.fixedLength(length);
-    for (int i = 0; i < length; i++) {
-      result[i] = JS('int', '#.charCodeAt(#)', this, i);
-    }
-    return result;
-  }
-
-  Iterable<int> get codeUnits => new CodeUnits(this);
+  List<int> get codeUnits => new CodeUnits(this);
 
   Runes get runes => new Runes(this);