Add asserts to ensure that we:

src/builtins.cc

Index: src/builtins.cc
===================================================================
--- src/builtins.cc	(revision 9277)
+++ src/builtins.cc	(working copy)
@@ -1621,6 +1621,7 @@
       // We pass all arguments to the generator, but it may not use all of
       // them.  This works because the first arguments are on top of the
       // stack.
+      ASSERT(!masm.has_frame());
       g(&masm, functions[i].name, functions[i].extra_args);
       // Move the code into the object heap.
       CodeDesc desc;