add fasta.scanner support for lazy assignment operators

pkg/front_end/test/scanner_roundtrip_test.dart

Index: pkg/front_end/test/scanner_roundtrip_test.dart
diff --git a/pkg/front_end/test/scanner_roundtrip_test.dart b/pkg/front_end/test/scanner_roundtrip_test.dart
index d731605b8b907c5a33c73ab5e2975a13021e9382..ab7e7297f8f7c1981f5a97cdb0739c3535fa78ba 100644
--- a/pkg/front_end/test/scanner_roundtrip_test.dart
+++ b/pkg/front_end/test/scanner_roundtrip_test.dart
@@ -44,22 +44,6 @@ class ScannerTest_RoundTrip extends ScannerTest {
 
   @override
   @failingTest
-  void test_ampersand_ampersand_eq() {
-    // TODO(paulberry,ahe): Fasta scanner doesn't support lazy assignment
-    // operators.
-    super.test_ampersand_ampersand_eq();
-  }
-
-  @override
-  @failingTest
-  void test_bar_bar_eq() {
-    // TODO(paulberry,ahe): Fasta scanner doesn't support lazy assignment
-    // operators.
-    super.test_bar_bar_eq();
-  }
-
-  @override
-  @failingTest
   void test_comment_generic_method_type_assign() {
     // TODO(paulberry,ahe): Fasta scanner doesn't support generic comment
     // syntax.