dart2js: add compiler builtins to the core-runtime.

pkg/compiler/lib/src/js_emitter/code_emitter_task.dart

Index: pkg/compiler/lib/src/js_emitter/code_emitter_task.dart
diff --git a/pkg/compiler/lib/src/js_emitter/code_emitter_task.dart b/pkg/compiler/lib/src/js_emitter/code_emitter_task.dart
index dc2236886dbd2544b864c1d693e197cd124ab78f..23c282ef27df1b22a462335d8bc06a5621aa5c12 100644
--- a/pkg/compiler/lib/src/js_emitter/code_emitter_task.dart
+++ b/pkg/compiler/lib/src/js_emitter/code_emitter_task.dart
@@ -124,6 +124,11 @@ class CodeEmitterTask extends CompilerTask {
     return emitter.typeAccess(e);
   }
 
+  /// Returns the JS template for the given [builtin].
+  jsAst.Template builtinTemplateFor(JsBuiltin builtin) {
+    return emitter.templateForBuiltin(builtin);
+  }
+
   void registerReadTypeVariable(TypeVariableElement element) {
     readTypeVariables.add(element);
   }
@@ -449,5 +454,8 @@ abstract class Emitter {
   /// Returns the JS code for accessing the given [constant].
   jsAst.Expression constantReference(ConstantValue constant);
 
+  /// Returns the JS template for the given [builtin].
+  jsAst.Template templateForBuiltin(JsBuiltin builtin);
+
   void invalidateCaches();
 }