[es6] implement default parameters via desugaring

test/mjsunit/harmony/default-parameters-lazy.js

Index: test/mjsunit/harmony/default-parameters-lazy.js
diff --git a/test/mjsunit/harmony/default-parameters-lazy.js b/test/mjsunit/harmony/default-parameters-lazy.js
new file mode 100644
index 0000000000000000000000000000000000000000..cabd4525f92d3f163b056460d1ddafb7dcedfb62
--- /dev/null
+++ b/test/mjsunit/harmony/default-parameters-lazy.js
@@ -0,0 +1,69 @@
+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --harmony-default-parameters --harmony-arrow-functions
+
+var i = 0;
+function f(handler = function(b) { return b + "#" + (++i); }, b = "red") {
+/* ............................................................................

[arv (Not doing code reviews), 2015/05/26 19:13:26]

I think there is a command line option that allows you to always use lazy
parsing.

[caitp (gmail), 2015/05/26 19:36:29]

It looks like you can disable lazy parsing/compilation, but you can't force it.

+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ * ............................................................................
+ */
+  return handler(b);
+}
+
+assertEquals([
+  "blue#1",
+  "red#2",
+  "red",
+  "yellow#3"
+], [
+  f(undefined, "blue"),
+  f(),
+  f(function(b) { return b; }),
+  f(undefined, "yellow")
+]);