Make JavaScriptBackend.processAnnotations element-model agnostic

pkg/compiler/lib/src/resolution/resolution_strategy.dart

 // Copyright (c) 2017, 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.
 
 library dart2js.resolution_strategy;
 
 import '../common.dart';
 import '../common_elements.dart';
 import '../common/backend_api.dart';
 import '../common/names.dart';
 import '../common/resolution.dart';
 import '../common/tasks.dart';
+import '../compiler.dart';
 import '../constants/values.dart';
-import '../compiler.dart';
 import '../elements/elements.dart';
 import '../elements/entities.dart';
 import '../elements/modelx.dart';
 import '../elements/resolution_types.dart';
 import '../environment.dart';
 import '../enqueue.dart';
 import '../frontend_strategy.dart';
 import '../js_backend/backend.dart';
 import '../js_backend/backend_usage.dart';
 import '../js_backend/custom_elements_analysis.dart';
@@ skipping 393 matching lines @@
   @override
   ResolutionFunctionType getLocalFunctionType(LocalFunctionElement function) {
     return function.type;
   }
 
   @override
   ResolutionDartType getUnaliasedType(ResolutionDartType type) {
     type.computeUnaliased(_resolution);
     return type.unaliased;
   }
+
+  @override
+  Iterable<ConstantValue> getMemberMetadata(MemberElement element) {
+    List<ConstantValue> values = <ConstantValue>[];
+    _compiler.reporter.withCurrentElement(element, () {
+      for (MetadataAnnotation metadata in element.implementation.metadata) {
+        metadata.ensureResolved(_compiler.resolution);
+        assert(invariant(metadata, metadata.constant != null,
+            message: "Unevaluated metadata constant."));
+        ConstantValue value =
+            _compiler.constants.getConstantValue(metadata.constant);
+        values.add(value);
+      }
+    });
+    return values;
+  }
 }
 
 /// AST-based logic for processing annotations. These annotations are processed
 /// very early in the compilation pipeline, typically this is before resolution
 /// is complete. Because of that this processor does a lightweight parse of the
 /// annotation (which is restricted to a limited subset of the annotation
 /// syntax), and, once resolution completes, it validates that the parsed
 /// annotations correspond to the correct element.
 class _ElementAnnotationProcessor implements AnnotationProcessor {
   Compiler _compiler;
@@ skipping 173 matching lines @@
             }
           }
         });
       });
     }
 
     _compiler.libraryLoader.libraries
         .forEach(processJsInteropAnnotationsInLibrary);
   }
 }