dart2js: patch file support cleanup

pkg/compiler/lib/src/ssa/graph_builder.dart

 // Copyright (c) 2016, 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.
 
 import '../closure.dart';
 import '../constants/constant_system.dart';
 import '../common/codegen.dart' show CodegenRegistry;
 import '../common_elements.dart';
 import '../compiler.dart';
 import '../deferred_load.dart';
@@ skipping 263 matching lines @@
     block.addSuccessor(newBlock);
     open(newBlock);
   }
 
   HInstruction callSetRuntimeTypeInfo(
       HInstruction typeInfo, HInstruction newObject);
 
   /// The element for which this SSA builder is being used.
   Element get targetElement;
   TypeBuilder get typeBuilder;
+
+  /// Helper to implement JS_GET_FLAG.
+  ///
+  /// The concrete SSA graph builder will extract a flag parameter from the
+  /// JS_GET_FLAG call and then push a boolean result onto the stack. This
+  /// function provides the boolean value corresponding to the given [flagName].
+  /// If [flagName] is not recognized, this function returns `null` and the
+  /// concrete SSA builder reports an error.
+  bool getFlagValue(String flagName) {
+    switch (flagName) {
+      case 'MUST_RETAIN_METADATA':
+        return mirrorsData.mustRetainMetadata;
+      case 'USE_CONTENT_SECURITY_POLICY':
+        return options.useContentSecurityPolicy;
+      case 'IS_FULL_EMITTER':
+        return !USE_LAZY_EMITTER && !options.useStartupEmitter;
+      default:
+        return null;
+    }
+  }
 }