Add a command line option to use the new CPS based backend.

pkg/compiler/lib/src/dart_backend/backend_ast_to_frontend_ast.dart

Index: pkg/compiler/lib/src/dart_backend/backend_ast_to_frontend_ast.dart
diff --git a/pkg/compiler/lib/src/dart_backend/backend_ast_to_frontend_ast.dart b/pkg/compiler/lib/src/dart_backend/backend_ast_to_frontend_ast.dart
index b15a4e2fbb014e8263d92f0ac9b8ec6cf99545fc..454ee91dff1e2e859ce61f33e573ddeb0175694d 100644
--- a/pkg/compiler/lib/src/dart_backend/backend_ast_to_frontend_ast.dart
+++ b/pkg/compiler/lib/src/dart_backend/backend_ast_to_frontend_ast.dart
@@ -24,7 +24,7 @@ tree.Node emit(dart2js.TreeElementMapping treeElements,
 /// it emits. This helps indicate which functions were translated by the new
 /// backend.
 bool INSERT_NEW_BACKEND_COMMENT =
-    const bool.fromEnvironment('USE_NEW_BACKEND', defaultValue: false);
+    const bool.fromEnvironment("INSERT_NEW_BACKEND_COMMENT");

[Johnni Winther, 2015/04/16 09:17:05]

Isn't this used anywhere?

[karlklose, 2015/04/16 11:21:46]

No, it is used for debugging purposes.

 
 /// Converts backend ASTs to frontend ASTs.
 class TreePrinter {