Fix getFieldType to handle metadata and workaround bad types for setters called via mirrors.

pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/classes.dart

 // Copyright (c) 2015, 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.
 
 /// This library defines the operations that define and manipulate Dart
 /// classes.  Included in this are:
 ///   - Generics
 ///   - Class metadata
 ///   - Extension methods
 ///
@@ skipping 199 matching lines @@
   let sigObj = $type[$_methodSig];
   if (sigObj === void 0) return void 0;
   return sigObj[$name];
 })()''');
 
 getFieldType(type, name) => JS(
     '',
     '''(() => {
   let sigObj = $type[$_fieldSig];
   if (sigObj === void 0) return void 0;
-  return sigObj[$name];
+  let fieldType = sigObj[$name];
+  // workaround to handle metadata.
+  return (fieldType instanceof Array) ? fieldType[0] : fieldType;
 })()''');
 
 getSetterType(type, name) => JS(
     '',
     '''(() => {
   let sigObj = $type[$_setterSig];
   if (sigObj === void 0) return void 0;
   return sigObj[$name];
 })()''');
 
@@ skipping 386 matching lines @@
     '''(() => {
   let values = [];
   for (var i = 0; i < $names.length; i++) {
     let value = $const_(new $enumClass(i));
     values.push(value);
     Object.defineProperty($enumClass, $names[i],
         { value: value, configurable: true });
   }
   $enumClass.values = $constList(values, $enumClass);
 })()''');