Implement is-checks against type variables.

sdk/lib/_internal/compiler/implementation/world.dart

Index: sdk/lib/_internal/compiler/implementation/world.dart
diff --git a/sdk/lib/_internal/compiler/implementation/world.dart b/sdk/lib/_internal/compiler/implementation/world.dart
index d2a03884a251bc0d09d1aeed5a8646b62c70a063..f3ce0a1f2c520f5cdf5e000260d16404e0978e7b 100644
--- a/sdk/lib/_internal/compiler/implementation/world.dart
+++ b/sdk/lib/_internal/compiler/implementation/world.dart
@@ -13,6 +13,7 @@ class World {
   final Map<ClassElement, Set<ClassElement>> rtiDependencies;
   final FunctionSet userDefinedGetters;
   final FunctionSet userDefinedSetters;
+  Link<ClassElement> classesUsingTypeVariableTests;
 
   World(Compiler compiler)
       : subtypes = new Map<ClassElement, Set<ClassElement>>(),
@@ -23,6 +24,7 @@ class World {
         userDefinedSetters = new FunctionSet(compiler),
         classesNeedingRti = new Set<ClassElement>(),
         rtiDependencies = new Map<ClassElement, Set<ClassElement>>(),
+        classesUsingTypeVariableTests = const Link<ClassElement>(),
         this.compiler = compiler;
 
   void populate() {
@@ -219,6 +221,16 @@ class World {
     }
     return result;
   }
+
+  /**
+   * Register a class that contains an is-test against one of it type variables.
+   * The class and all its subtypes need runtime type information and we need to
+   * register the type arguments of their instantiations.
+   */
+  registerTypeVariableCheck(ClassElement cls) {
+    classesUsingTypeVariableTests = classesUsingTypeVariableTests.prepend(cls);
+    classesNeedingRti.add(cls);
+  }
 }
 
 /**