Implement the new '??' operator in analyzer.

pkg/analyzer/test/generated/engine_test.dart

Index: pkg/analyzer/test/generated/engine_test.dart
diff --git a/pkg/analyzer/test/generated/engine_test.dart b/pkg/analyzer/test/generated/engine_test.dart
index 579aaf30543b1891150b26516025ae4c0635c50d..88daa183f30e81f1fc86bda0e422585d03f42363 100644
--- a/pkg/analyzer/test/generated/engine_test.dart
+++ b/pkg/analyzer/test/generated/engine_test.dart
@@ -2221,6 +2221,7 @@ class AnalysisOptionsImplTest extends EngineTestCase {
       options.analyzeFunctionBodies = booleanValue;
       options.cacheSize = i;
       options.dart2jsHint = booleanValue;
+      options.enableNullAwareOperators = booleanValue;
       options.enableStrictCallChecks = booleanValue;
       options.generateImplicitErrors = booleanValue;
       options.generateSdkErrors = booleanValue;
@@ -2231,6 +2232,7 @@ class AnalysisOptionsImplTest extends EngineTestCase {
       expect(copy.analyzeFunctionBodies, options.analyzeFunctionBodies);
       expect(copy.cacheSize, options.cacheSize);
       expect(copy.dart2jsHint, options.dart2jsHint);
+      expect(copy.enableNullAwareOperators, options.enableNullAwareOperators);
       expect(copy.enableStrictCallChecks, options.enableStrictCallChecks);
       expect(copy.generateImplicitErrors, options.generateImplicitErrors);
       expect(copy.generateSdkErrors, options.generateSdkErrors);