Generate tear-off closures dynamically.

dart/sdk/lib/_internal/compiler/implementation/js_emitter/metadata_emitter.dart

Index: dart/sdk/lib/_internal/compiler/implementation/js_emitter/metadata_emitter.dart
diff --git a/dart/sdk/lib/_internal/compiler/implementation/js_emitter/metadata_emitter.dart b/dart/sdk/lib/_internal/compiler/implementation/js_emitter/metadata_emitter.dart
index 6fb21d33098f5aeeee2ffdad53fd302aee7c1aa9..fc7f47f37a401f0baa25b7eb70fa323f5a2785d4 100644
--- a/dart/sdk/lib/_internal/compiler/implementation/js_emitter/metadata_emitter.dart
+++ b/dart/sdk/lib/_internal/compiler/implementation/js_emitter/metadata_emitter.dart
@@ -42,9 +42,9 @@ class MetadataEmitter extends CodeEmitterHelper {
     });
   }
 
-  jsAst.Node reifyDefaultArguments(FunctionElement function) {
+  List<int> reifyDefaultArguments(FunctionElement function) {
     FunctionSignature signature = function.computeSignature(compiler);
-    if (signature.optionalParameterCount == 0) return null;
+    if (signature.optionalParameterCount == 0) return const [];
     List<int> defaultValues = <int>[];
     for (Element element in signature.orderedOptionalParameters) {
       Constant value =
@@ -55,7 +55,7 @@ class MetadataEmitter extends CodeEmitterHelper {
               .getText();
       defaultValues.add(addGlobalMetadata(stringRepresentation));
     }
-    return js.toExpression(defaultValues);
+    return defaultValues;
   }
 
   int reifyMetadata(MetadataAnnotation annotation) {
@@ -118,21 +118,19 @@ class MetadataEmitter extends CodeEmitterHelper {
     buffer.write('];$n');
   }
 
+  // TODO(ahe): Delete this method.
   jsAst.Fun extendWithMetadata(FunctionElement element, jsAst.Fun code) {
     if (!backend.retainMetadataOf(element)) return code;
+    List<int> metadata = computeMetadata(element, true);
+    code.body.statements.add(js.string(metadata.join(',')).toStatement());
+    return code;
+  }
+
+  // TODO(ahe): Remove optional argument.
+  List<int> computeMetadata(FunctionElement element, [bool includeNames = false]) {
     return compiler.withCurrentElement(element, () {
+      if (!backend.retainMetadataOf(element)) return const <int>[];
       List<int> metadata = <int>[];
-      FunctionSignature signature = element.functionSignature;
-      if (element.isConstructor()) {
-        metadata.add(reifyType(element.getEnclosingClass().thisType));
-      } else {
-        metadata.add(reifyType(signature.returnType));
-      }
-      signature.forEachParameter((Element parameter) {
-        metadata
-            ..add(reifyName(parameter.name))
-            ..add(reifyType(parameter.computeType(compiler)));
-      });
       Link link = element.metadata;
       // TODO(ahe): Why is metadata sometimes null?
       if (link != null) {
@@ -140,8 +138,7 @@ class MetadataEmitter extends CodeEmitterHelper {
           metadata.add(reifyMetadata(link.head));
         }
       }
-      code.body.statements.add(js.string(metadata.join(',')).toStatement());
-      return code;
+      return metadata;
     });
   }
 }