Support checking of malbounded types.

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

Index: sdk/lib/_internal/compiler/implementation/compiler.dart
diff --git a/sdk/lib/_internal/compiler/implementation/compiler.dart b/sdk/lib/_internal/compiler/implementation/compiler.dart
index 61638b4fa5e7d3092eecea3bc14ba6181e3b0940..0a96d2256d8f0a786e630cacff3260da90d60ce0 100644
--- a/sdk/lib/_internal/compiler/implementation/compiler.dart
+++ b/sdk/lib/_internal/compiler/implementation/compiler.dart
@@ -174,6 +174,14 @@ abstract class Backend {
                        Enqueuer enqueuer,
                        TreeElements elements) {}
 
+  /// Register a runtime type variable bound tests between [typeArgument] and
+  /// [bound].
+  void registerTypeVariableBoundsSubtypeCheck(DartType typeArgument,
+                                              DartType bound) {}
+
+  /// Registers that a type variable bounds check might occur at runtime.
+  void registerTypeVariableBoundCheck(TreeElements elements) {}
+
   /// Register that the application may throw a [NoSuchMethodError].
   void registerThrowNoSuchMethod(TreeElements elements) {}