Rename Type to DartType to avoid conflicts with the class Type in the core library.

lib/compiler/implementation/closure.dart

Index: lib/compiler/implementation/closure.dart
diff --git a/lib/compiler/implementation/closure.dart b/lib/compiler/implementation/closure.dart
index 6782e1585c1404e3071146afd4283ef39634e8f7..f278e6ba8ba7b5118f37e1dcb0d93a0f15ef6f9b 100644
--- a/lib/compiler/implementation/closure.dart
+++ b/lib/compiler/implementation/closure.dart
@@ -70,8 +70,8 @@ class ClosureClassElement extends ClassElement {
               STATE_DONE) {
     compiler.closureClass.ensureResolved(compiler);
     supertype = compiler.closureClass.computeType(compiler);
-    interfaces = const EmptyLink<Type>();
-    allSupertypes = new Link<Type>(supertype);
+    interfaces = const EmptyLink<DartType>();
+    allSupertypes = new Link<DartType>(supertype);
   }
   bool isClosure() => true;
 }