dart2js cps: Clean up and avoid processing unreachable code.

pkg/compiler/lib/src/js_backend/codegen/unsugar.dart

 library dart2js.unsugar_cps;
 
 import '../../cps_ir/cps_ir_nodes.dart';
 
 import '../../cps_ir/optimizers.dart' show ParentVisitor, Pass;
 import '../../constants/values.dart';
 import '../../elements/elements.dart';
 import '../../js_backend/codegen/glue.dart';
 import '../../universe/selector.dart' show Selector;
 import '../../cps_ir/cps_ir_builder.dart' show ThisParameterLocal;
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     // Rethrow can only appear in a catch block.  It throws that block's
     // (wrapped) caught exception.
     Throw replacement = new Throw(_exceptionParameter);
     InteriorNode parent = node.parent;
     parent.body = replacement;
     replacement.parent = parent;
     // The original rethrow does not have any references that we need to
     // worry about unlinking.
   }
 
-  // TODO(24523): Insert interceptor on demand when we discover we want to use
-  // one rather than on every check.
-  processTypeTest(TypeTest node) {
-    assert(node.interceptor == null);
-    Primitive receiver = node.value.definition;
-    Primitive interceptor = new Interceptor(receiver, node.sourceInformation)
-        ..interceptedClasses.addAll(_glue.interceptedClasses);
-    new LetPrim(interceptor).insertAbove(node.parent);
-    node.interceptor = new Reference<Primitive>(interceptor);
-    node.interceptor.parent = node;
-  }
-
   bool isNullConstant(Primitive prim) {
     return prim is Constant && prim.value.isNull;
   }
 
   processInvokeMethod(InvokeMethod node) {
     Selector selector = node.selector;
     if (!_glue.isInterceptedSelector(selector)) return;
 
     // Some platform libraries will compare non-interceptable objects against
     // null using the Dart == operator.  These must be translated directly.
@@ skipping 50 matching lines @@
     }
     node.arguments.insert(0, node.receiver);
     node.receiver = new Reference<Primitive>(newReceiver)..parent = node;
     node.callingConvention = CallingConvention.Intercepted;
   }
 
   processInterceptor(Interceptor node) {
     _glue.registerSpecializedGetInterceptor(node.interceptedClasses);
   }
 }