Implement is-checks against type variables.

sdk/lib/_internal/compiler/implementation/resolution/members.dart

Index: sdk/lib/_internal/compiler/implementation/resolution/members.dart
diff --git a/sdk/lib/_internal/compiler/implementation/resolution/members.dart b/sdk/lib/_internal/compiler/implementation/resolution/members.dart
index 7e069cc75aee3c54f8305815a103efd8c969c919..df901a433a2c59323ac671c7a6aab432504a255f 100644
--- a/sdk/lib/_internal/compiler/implementation/resolution/members.dart
+++ b/sdk/lib/_internal/compiler/implementation/resolution/members.dart
@@ -2427,7 +2427,7 @@ class ResolverVisitor extends CommonResolverVisitor<Element> {
     ClassElement cls = constructor.defaultImplementation.getEnclosingClass();
     // [cls] might be the implementation element and only declaration elements
     // may be registered.
-    world.registerInstantiatedClass(cls.declaration);
+    world.registerInstantiatedType(mapping.getType(node));
     if (cls.isAbstract(compiler)) {
       compiler.backend.registerAbstractClassInstantiation();
     }
@@ -2497,9 +2497,7 @@ class ResolverVisitor extends CommonResolverVisitor<Element> {
           analyzeTypeArgument(type, argument);
         });
       }
-      // TODO(ngeoffray): Also handle cases like:
-      // 1) a is T
-      // 2) T a (in checked mode).
+      // TODO(ngeoffray): Also handle T a (in checked mode).
     }
     return type;
   }