Remove deprecated string features.

tests/language/instance_inline_test.dart

Index: tests/language/instance_inline_test.dart
diff --git a/tests/language/instance_inline_test.dart b/tests/language/instance_inline_test.dart
index e45dde29f53bbc92b0f3833749f23081c65ea71f..fefdf21ae19def9321b94d5854fcbeaa51e938e2 100644
--- a/tests/language/instance_inline_test.dart
+++ b/tests/language/instance_inline_test.dart
@@ -15,7 +15,7 @@ class StringScanner {
   int nextByte() => charAt(++byteOffset);
 
   int charAt(index)
-      => (string.length > index) ? string.charCodeAt(index) : -1;
+      => (string.length > index) ? string.codeUnitAt(index) : -1;
 }
 
 void main() {
@@ -24,4 +24,4 @@ void main() {
   Expect.equals(0x7A, scanner.nextByte()); // Expect z.
   Expect.equals(0x39, scanner.nextByte()); // Expect 9.
   Expect.equals(-1, scanner.nextByte());
-}
+}