Fixes a couple problems with GC of unoptimized code.

runtime/vm/intermediate_language.h

Index: runtime/vm/intermediate_language.h
===================================================================
--- runtime/vm/intermediate_language.h	(revision 30197)
+++ runtime/vm/intermediate_language.h	(working copy)
@@ -6847,6 +6847,8 @@
 
   const Function& function() const { return function_; }
 
+  const Code& code() const { return code_; }
+
   Environment* DeepCopy() const { return DeepCopy(Length()); }
 
   void DeepCopyTo(Instruction* instr) const;
@@ -6867,6 +6869,7 @@
         fixed_parameter_count_(fixed_parameter_count),
         deopt_id_(deopt_id),
         function_(function),
+        code_(Code::Handle(function.unoptimized_code())),
         outer_(outer) { }
 
   // Deep copy an environment.  The 'length' parameter may be less than the
@@ -6879,6 +6882,7 @@
   const intptr_t fixed_parameter_count_;
   intptr_t deopt_id_;
   const Function& function_;
+  const Code& code_;
   Environment* outer_;
 
   DISALLOW_COPY_AND_ASSIGN(Environment);