add fasta.scanner support for lazy assignment operators

pkg/analyzer/lib/src/dart/scanner/scanner.dart

Index: pkg/analyzer/lib/src/dart/scanner/scanner.dart
diff --git a/pkg/analyzer/lib/src/dart/scanner/scanner.dart b/pkg/analyzer/lib/src/dart/scanner/scanner.dart
index 77c84c92e8a4bad20d4b818b6a1c2a0dc6da9947..1a78ccfb4bbeaa183e99182fd1e6337cf7c76625 100644
--- a/pkg/analyzer/lib/src/dart/scanner/scanner.dart
+++ b/pkg/analyzer/lib/src/dart/scanner/scanner.dart
@@ -147,8 +147,9 @@ class _Scanner2 implements Scanner {
       // TODO(danrubel): remove this once fasts support has been added.
       throw 'No generic method comment support in Fasta';
     }
-    fasta.ScannerResult result =
-        fasta.scanString(_contents, includeComments: _preserveComments);
+    fasta.ScannerResult result = fasta.scanString(_contents,
+        includeComments: _preserveComments,
+        scanLazyAssignmentOperators: scanLazyAssignmentOperators);
     // fasta pretends there is an additional line at EOF
     lineStarts
         .addAll(result.lineStarts.sublist(1, result.lineStarts.length - 1));