Introduce an ElementTypeMask to recognize simple constraints like "the type of parameter foo is the…

sdk/lib/_internal/compiler/implementation/types/concrete_types_inferrer.dart

Index: sdk/lib/_internal/compiler/implementation/types/concrete_types_inferrer.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/types/concrete_types_inferrer.dart	(revision 24183)
+++ sdk/lib/_internal/compiler/implementation/types/concrete_types_inferrer.dart	(working copy)
@@ -474,6 +474,14 @@
     throw new UnsupportedError("");
   }
 
+  bool get isForwarding {
+    throw new UnsupportedError("");
+  }
+
+  bool get isElement {
+    throw new UnsupportedError("");
+  }
+
   bool containsOnlyInt(Compiler compiler) {
     throw new UnsupportedError("");
   }