Create a Tree IR builder for JavaScript specific nodes.

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

Index: pkg/compiler/lib/src/js_backend/codegen/js_tree_builder.dart
diff --git a/pkg/compiler/lib/src/js_backend/codegen/js_tree_builder.dart b/pkg/compiler/lib/src/js_backend/codegen/js_tree_builder.dart
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index 0000000000000000000000000000000000000000..32dde10d0725e8135eba27812b8f0af8cf3040a1
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+++ b/pkg/compiler/lib/src/js_backend/codegen/js_tree_builder.dart
@@ -0,0 +1,51 @@
+// Copyright (c) 2014, 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 js_tree_ir_builder;
+
+import '../../tree_ir/tree_ir_builder.dart' show Builder;
+import 'glue.dart' show Glue;
+import '../../dart2jslib.dart' show Selector, InternalErrorFunction;
+import '../../elements/elements.dart';
+import '../../cps_ir/cps_ir_nodes.dart' as cps_ir;
+import '../../tree_ir/tree_ir_nodes.dart';
+
+/// Subclass of [Builder] that can translate nodes which are specific to the
+/// JavaScript backend.
+class JsTreeBuilder extends Builder {
+  final Glue _glue;
+  final Element identicalFunction;
+
+  JsTreeBuilder(
+      InternalErrorFunction internalError,
+      this.identicalFunction,
+      this._glue,
+      [Builder parent])
+    : super(internalError, parent);
+
+  JsTreeBuilder createInnerBuilder() {
+    return new JsTreeBuilder(internalError, identicalFunction, _glue, this);
+  }
+
+  Selector get identicalSelector {
+    return new Selector.call('identical', null, 2);
+  }
+
+  Expression visitIdentical(cps_ir.Identical node) {
+    return new InvokeStatic(
+        identicalFunction,
+        identicalSelector,
+        <Expression>[getVariableReference(node.left),
+                     getVariableReference(node.right)]);
+  }
+
+  Expression visitInterceptor(cps_ir.Interceptor node) {
+    Element getInterceptor = _glue.getInterceptorMethod;
+    _glue.registerUseInterceptorInCodegen();
+    return new InvokeStatic(
+        getInterceptor,
+        new Selector.fromElement(getInterceptor),
+        <Expression>[getVariableReference(node.input)]);
+  }
+}