Remove flag for enabling null-aware operators. They are now on by default.

pkg/compiler/lib/src/scanner/utf8_bytes_scanner.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of scanner;
 
 /**
  * Scanner that reads from a UTF-8 encoded list of bytes and creates tokens
  * that points to substrings.
  */
@@ skipping 51 matching lines @@
 
   /**
    * Creates a new Utf8BytesScanner. The source file is expected to be a
    * [Utf8BytesSourceFile] that holds a list of UTF-8 bytes. Otherwise the
    * string text of the source file is decoded.
    *
    * The list of UTF-8 bytes [file.slowUtf8Bytes()] is expected to return an
    * array whose last element is '0' to signal the end of the file. If this
    * is not the case, the entire array is copied before scanning.
    */
-  Utf8BytesScanner(SourceFile file, {bool includeComments: false,
-                                     bool enableNullAwareOperators: false})
+  Utf8BytesScanner(SourceFile file, {bool includeComments: false})
       : bytes = file.slowUtf8ZeroTerminatedBytes(),
-        super(file, includeComments, enableNullAwareOperators) {
+        super(file, includeComments) {
     assert(bytes.last == 0);
     // Skip a leading BOM.
     if (_containsBomAt(0)) byteOffset += 3;
   }
 
   /**
    * Creates a new Utf8BytesScanner from a list of UTF-8 bytes.
    *
    * The last element of the list is expected to be '0' to signal the end of
    * the file. If this is not the case, the entire array is copied before
    * scanning.
    */
   Utf8BytesScanner.fromBytes(List<int> zeroTerminatedBytes,
-                             {bool includeComments: false,
-                              bool enableNullAwareOperators: false})
+                             {bool includeComments: false})
       : this.bytes = zeroTerminatedBytes,
-        super(null, includeComments, enableNullAwareOperators) {
+        super(null, includeComments) {
     assert(bytes.last == 0);
   }
 
   bool _containsBomAt(int offset) {
     const BOM_UTF8 = const [0xEF, 0xBB, 0xBF];
 
     return offset + 3 < bytes.length &&
         bytes[offset] == BOM_UTF8[0] &&
         bytes[offset + 1] == BOM_UTF8[1] &&
         bytes[offset + 2] == BOM_UTF8[2];
@@ skipping 97 matching lines @@
 
   void appendSubstringToken(PrecedenceInfo info, int start, bool asciiOnly,
                             [int extraOffset = 0]) {
     tail.next = new StringToken.fromUtf8Bytes(
         info, bytes, start, byteOffset + extraOffset, asciiOnly, tokenStart);
     tail = tail.next;
   }
 
   bool atEndOfFile() => byteOffset >= bytes.length - 1;
 }