Adjusts dart2js backend to handle method type arguments.

pkg/compiler/lib/src/resolution/signatures.dart

Index: pkg/compiler/lib/src/resolution/signatures.dart
diff --git a/pkg/compiler/lib/src/resolution/signatures.dart b/pkg/compiler/lib/src/resolution/signatures.dart
index 33a8f2f336bb0a62d8683a7c5e32d3a580581636..d3f3264e06a649e3dd7d7797e83ffc431c9934a0 100644
--- a/pkg/compiler/lib/src/resolution/signatures.dart
+++ b/pkg/compiler/lib/src/resolution/signatures.dart
@@ -314,10 +314,12 @@ class SignatureResolver extends MappingVisitor<FormalElementX> {
         nodes = nodes.tail;
         TypeVariableElementX variableElement =
             new TypeVariableElementX(variableName, element, index, node);
-        // TODO(eernst): When type variables are implemented fully we will need
-        // to resolve the actual bounds; currently we just claim [dynamic].
+        // GENERIC_METHODS: When method type variables are implemented fully we
+        // must resolve the actual bounds; currently we just claim that
+        // every method type variable has upper bound [dynamic].
         variableElement.boundCache = const DynamicType();
-        TypeVariableType variableType = new TypeVariableType(variableElement);
+        TypeVariableType variableType =
+            new MethodTypeVariableType(variableElement);
         variableElement.typeCache = variableType;
         return variableType;
       }, growable: false);