Clean up handling of constants in the CPS backend.

pkg/compiler/lib/src/use_unused_api.dart

 // Copyright (c) 2012, 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.
 
 /// This file use methods that aren't used by dart2js.dart, but that we wish to
 /// keep anyway. This might be general API that isn't currently in use,
 /// debugging aids, or API only used for testing (see TODO below).
 
 library dart2js.use_unused_api;
 
@@ skipping 235 matching lines @@
   pce.copyWithEnclosing(null);
   pfe.copyWithEnclosing(null);
 }
 
 useIr(ir_builder.IrBuilderTask task,
       ir_builder.IrBuilder builder) {
   task
     ..hasIr(null)
     ..getIr(null);
   builder
-    ..buildIntegerLiteral(null)
-    ..buildDoubleLiteral(null)
-    ..buildBooleanLiteral(null)
-    ..buildNullLiteral()
-    ..buildStringLiteral(null)
+    ..buildStringConstant(null)
     ..buildDynamicGet(null, null);
 }
 
 useCompiler(dart2jslib.Compiler compiler) {
   compiler.libraryLoader
       ..reset()
       ..resetAsync(null)
       ..lookupLibrary(null);
   compiler.forgetElement(null);
 }
@@ skipping 30 matching lines @@
   visitFieldDefinition(tree_ir.FieldDefinition node) {}
 
   visitFieldInitializer(tree_ir.FieldInitializer node) {}
   visitSuperInitializer(tree_ir.SuperInitializer node) {}
 }
 
 useTreeVisitors() {
   new DummyTreeVisitor().visitRootNode(null);
   new DummyTreeVisitor().visitInitializer(null);
 }