Unify parsing of constructor references.

dart/lib/compiler/implementation/typechecker.dart

Index: dart/lib/compiler/implementation/typechecker.dart
diff --git a/dart/lib/compiler/implementation/typechecker.dart b/dart/lib/compiler/implementation/typechecker.dart
index 36e176c17aaf4c91eb1e4ac52ad8c605ff248236..ac2025621e8cc9f5f7772f2a091021907f2c24be 100644
--- a/dart/lib/compiler/implementation/typechecker.dart
+++ b/dart/lib/compiler/implementation/typechecker.dart
@@ -70,6 +70,8 @@ abstract class DartType {
   abstract DartType unalias(Compiler compiler);
 
   abstract bool operator ==(other);
+
+  DartType asRaw() => this;
 }
 
 class TypeVariableType implements DartType {
@@ -186,6 +188,11 @@ class InterfaceType implements DartType {
     if (!identical(element, other.element)) return false;
     return arguments == other.arguments;
   }
+
+  InterfaceType asRaw() {
+    if (arguments.isEmpty) return this;
+    return new InterfaceType(element);
+  }
 }
 
 class FunctionType implements DartType {