dart2js cps: Fix some analyzer hints in the CPS backend.

pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 library dart2js.ir_nodes;
 
 import 'dart:collection';
 import 'cps_fragment.dart' show CpsFragment;
 import '../constants/values.dart' as values;
 import '../dart_types.dart' show DartType, InterfaceType, TypeVariableType;
 import '../elements/elements.dart';
@@ skipping 2445 matching lines @@
   List<Definition> getList(List<Reference> list) => list.map(getCopy).toList();
 
   /// Copy a non-[Continuation] [Definition].
   Definition copy(Definition node) {
     assert (node is! Continuation);
     return putCopy(node, visit(node));
   }
 
   Definition visit(Node node) => node.accept(this);
 
-  Definition visitFunctionDefinition(FunctionDefinition node) {}
-  Definition visitLetPrim(LetPrim node) {}
-  Definition visitLetCont(LetCont node) {}
-  Definition visitLetHandler(LetHandler node) {}
-  Definition visitLetMutable(LetMutable node) {}
-  Definition visitInvokeContinuation(InvokeContinuation node) {}
-  Definition visitThrow(Throw node) {}
-  Definition visitRethrow(Rethrow node) {}
-  Definition visitBranch(Branch node) {}
-  Definition visitUnreachable(Unreachable node) {}
-  Definition visitContinuation(Continuation node) {}
+  visitFunctionDefinition(FunctionDefinition node) {}
+  visitLetPrim(LetPrim node) {}
+  visitLetCont(LetCont node) {}
+  visitLetHandler(LetHandler node) {}
+  visitLetMutable(LetMutable node) {}
+  visitInvokeContinuation(InvokeContinuation node) {}
+  visitThrow(Throw node) {}
+  visitRethrow(Rethrow node) {}
+  visitBranch(Branch node) {}
+  visitUnreachable(Unreachable node) {}
+  visitContinuation(Continuation node) {}
 
   Definition visitInvokeStatic(InvokeStatic node) {
     return new InvokeStatic(node.target, node.selector, getList(node.arguments),
         node.sourceInformation);
   }
 
   Definition visitInvokeMethod(InvokeMethod node) {
     return new InvokeMethod(getCopy(node.receiver), node.selector, node.mask,
         getList(node.arguments),
         node.sourceInformation);
@@ skipping 282 matching lines @@
   // Tail expressions do not have references, so we do not need to map them
   // to their copies.
   visitInvokeContinuation(InvokeContinuation node) {
     plug(new InvokeContinuation(_copies[node.continuation.definition],
         _definitions.getList(node.arguments),
         isRecursive: node.isRecursive,
         isEscapingTry: node.isEscapingTry,
         sourceInformation: node.sourceInformation));
   }
 
-  Node visitThrow(Throw node) {
+  visitThrow(Throw node) {
     plug(new Throw(_definitions.getCopy(node.value)));
   }
 
-  Node visitRethrow(Rethrow node) {
+  visitRethrow(Rethrow node) {
     plug(new Rethrow());
   }
 
-  Node visitBranch(Branch node) {
+  visitBranch(Branch node) {
     plug(new Branch.loose(_definitions.getCopy(node.condition),
         _copies[node.trueContinuation.definition],
         _copies[node.falseContinuation.definition])
       ..isStrictCheck = node.isStrictCheck);
   }
 
-  Node visitUnreachable(Unreachable node) {
+  visitUnreachable(Unreachable node) {
     plug(new Unreachable());
   }
 }