Add helpers library to dart2js.

sdk/lib/_internal/compiler/implementation/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;
 
+import '../compiler.dart' as api;
+
 import 'dart2js.dart' as dart2js;
 
 import 'dart2jslib.dart' as dart2jslib;
 
 import 'tree/tree.dart' as tree;
 
 import 'util/util.dart' as util;
 
 import 'elements/elements.dart' as elements;
 
@@ skipping 10 matching lines @@
 import 'dart_types.dart' as dart_types;
 
 import 'universe/universe.dart' as universe;
 
 import 'inferrer/type_graph_inferrer.dart' as type_graph_inferrer;
 
 import 'source_file_provider.dart' as source_file_provider;
 
 import 'ssa/ssa.dart' as ssa;
 
+import 'ir/ir_nodes.dart' as ir_nodes;
+
+import 'ir/ir_builder.dart' as ir_builder;
+
 class ElementVisitor extends elements_visitor.ElementVisitor {
   visitElement(e) {}
 }
 
 void main(List<String> arguments) {
+  useApi();
   dart2js.main(arguments);
   useConstant(null, null);
   useNode(null);
   useUtil(null);
   useElementVisitor(new ElementVisitor());
   useJs(new js.Program(null));
   useJs(new js.Blob(null));
   useJs(new js.NamedFunction(null, null));
   useConcreteTypesInferrer(null);
   useColor();
   useFilenames();
   useSsa(null);
   useCodeBuffer(null);
   usedByTests();
   useElements(null, null);
+  useIr(null, null);
+}
+
+useApi() {
+  api.ReadStringFromUri uri;
 }
 
 void useConstant(dart2jslib.Constant constant, dart2jslib.ConstantSystem cs) {
   constant.isObject;
   cs.isBool(constant);
 }
 
 void useNode(tree.Node node) {
   node
     ..asBreakStatement()
@@ skipping 31 matching lines @@
     ..asSwitchStatement()
     ..asTryStatement()
     ..asTypeAnnotation()
     ..asTypeVariable()
     ..asTypedef()
     ..asWhile();
 }
 
 void useUtil(util.Link link) {
   link.reversePrependAll(link);
-  util.trace("");
 }
 
 void useElementVisitor(ElementVisitor visitor) {
   visitor
     ..visit(null)
     ..visitAbstractFieldElement(null)
     ..visitAmbiguousElement(null)
     ..visitBoxElement(null)
     ..visitBoxFieldElement(null)
     ..visitClassElement(null)
@@ skipping 49 matching lines @@
 useCodeBuffer(dart2jslib.CodeBuffer buffer) {
   buffer.writeln();
 }
 
 usedByTests() {
   // TODO(ahe): We should try to avoid including API used only for tests. In
   // most cases, such API can be moved to a test library.
   dart2jslib.World world = null;
   dart2jslib.Compiler compiler = null;
   compiler.currentlyInUserCode();
-  compiler.inUserCode(null);
   type_graph_inferrer.TypeGraphInferrer typeGraphInferrer = null;
   source_file_provider.SourceFileProvider sourceFileProvider = null;
   world.hasAnyUserDefinedGetter(null);
   compiler.importHelperLibrary(null);
   typeGraphInferrer.getCallersOf(null);
   dart_types.Types.sorted(null);
   new universe.TypedSelector.subclass(null, null);
   new universe.TypedSelector.subtype(null, null);
   new universe.TypedSelector.exact(null, null);
   sourceFileProvider.readStringFromUri(null);
 }
 
 useElements(elements.ClassElement e, elements.Name n) {
   e.lookupClassMember(null);
   e.lookupInterfaceMember(null);
   n.isAccessibleFrom(null);
+}
+
+useIr(ir_nodes.SExpressionStringifier stringifier,
+      ir_builder.IrBuilderTask task) {
+  new ir_nodes.SExpressionStringifier();
+  stringifier
+    ..newContinuationName()
+    ..newValueName()
+    ..visitConstant(null)
+    ..visitContinuation(null)
+    ..visitDefinition(null)
+    ..visitExpression(null)
+    ..visitFunction(null)
+    ..visitInvokeStatic(null)
+    ..visitLetCont(null)
+    ..visitLetVal(null)
+    ..visitNode(null)
+    ..visitParameter(null);
+  task
+    ..hasIr(null)
+    ..getIr(null);
 }