use symbol literals instead of const ctor in packages

pkg/polymer/lib/src/instance.dart

Index: pkg/polymer/lib/src/instance.dart
diff --git a/pkg/polymer/lib/src/instance.dart b/pkg/polymer/lib/src/instance.dart
index 67f577b6a8ae966b4489886376cfa0a9d17d421e..2fcf144f2c2dd0c10909e717970064d34fbc3a7a 100644
--- a/pkg/polymer/lib/src/instance.dart
+++ b/pkg/polymer/lib/src/instance.dart
@@ -334,11 +334,11 @@ class PolymerElement extends CustomElement with ObservableMixin {
     if (value == null) return null;
 
     final type = inferredType.qualifiedName;
-    if (type == const Symbol('dart.core.bool')) {
+    if (type == #dart.core.bool) {
       return _toBoolean(value) ? '' : null;
-    } else if (type == const Symbol('dart.core.String')
-        || type == const Symbol('dart.core.int')
-        || type == const Symbol('dart.core.double')) {
+    } else if (type == #dart.core.String
+        || type == #dart.core.int
+        || type == #dart.core.double) {
       return '$value';
     }
     return null;
@@ -361,7 +361,7 @@ class PolymerElement extends CustomElement with ObservableMixin {
       // refine the attr reflection system to achieve this; pica, for example,
       // relies on having inferredType object properties not removed as
       // attrs.
-    } else if (inferredType.qualifiedName == const Symbol('dart.core.bool')) {
+    } else if (inferredType.qualifiedName == #dart.core.bool) {
       attributes.remove(name);
     }
   }
@@ -910,8 +910,8 @@ TypeMirror _propertyType(DeclarationMirror property) =>
 
 TypeMirror _inferPropertyType(Object value, DeclarationMirror property) {
   var type = _propertyType(property);
-  if (type.qualifiedName == const Symbol('dart.core.Object') ||
-      type.qualifiedName == const Symbol('dynamic')) {
+  if (type.qualifiedName == #dart.core.Object ||
+      type.qualifiedName == #dynamic) {
     // Attempt to infer field type from the default value.
     if (value != null) {
       type = reflect(value).type;