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

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

Index: pkg/compiler/lib/src/scanner/utf8_bytes_scanner.dart
diff --git a/pkg/compiler/lib/src/scanner/utf8_bytes_scanner.dart b/pkg/compiler/lib/src/scanner/utf8_bytes_scanner.dart
index f242f57ebeaf10fad75a21b95e6cb10924c44602..d919596154580c9a6e09b6a710dfafb7142d9544 100644
--- a/pkg/compiler/lib/src/scanner/utf8_bytes_scanner.dart
+++ b/pkg/compiler/lib/src/scanner/utf8_bytes_scanner.dart
@@ -69,10 +69,9 @@ class Utf8BytesScanner extends ArrayBasedScanner {
    * 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;
@@ -86,10 +85,9 @@ class Utf8BytesScanner extends ArrayBasedScanner {
    * 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);
   }