dart2js: Fix check for support of reflection.

pkg/compiler/lib/src/js_emitter/code_emitter_task.dart

 // Copyright (c) 2012, 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.
 
 part of dart2js.js_emitter;
 
 const USE_LAZY_EMITTER = const bool.fromEnvironment("dart2js.use.lazy.emitter");
 const USE_STARTUP_EMITTER =
     const bool.fromEnvironment("dart2js.use.startup.emitter");
 
@@ skipping 134 matching lines @@
       return size;
     });
   }
 }
 
 abstract class Emitter {
   /// Uses the [programBuilder] to generate a model of the program, emits
   /// the program, and returns the size of the generated output.
   int emitProgram(ProgramBuilder programBuilder);
 
+  /// Returns true, if the emitter supports reflection.
+  bool get supportsReflection;
+
   /// Returns the JS function that must be invoked to get the value of the
   /// lazily initialized static.
   jsAst.Expression isolateLazyInitializerAccess(FieldElement element);
 
   /// Returns the closure expression of a static function.
   jsAst.Expression isolateStaticClosureAccess(FunctionElement element);
 
   /// Returns the JS code for accessing the embedded [global].
   jsAst.Expression generateEmbeddedGlobalAccess(String global);
 
@@ skipping 25 matching lines @@
   bool isConstantInlinedOrAlreadyEmitted(ConstantValue constant);
 
   /// Returns the JS code for accessing the given [constant].
   jsAst.Expression constantReference(ConstantValue constant);
 
   /// Returns the JS template for the given [builtin].
   jsAst.Template templateForBuiltin(JsBuiltin builtin);
 
   void invalidateCaches();
 }