Restore back pointer from Instructions to Code

runtime/vm/object.h

Index: runtime/vm/object.h
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index 8e4b24ed2981d54857c2e6d980d15e6774244fb5..934697ec3b3f7ed2a6493d5dfdf2b10aa11ea329 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -3714,6 +3714,13 @@ class Instructions : public Object {
  public:
   intptr_t size() const { return raw_ptr()->size_; }  // Excludes HeaderSize().
 
+  RawCode* code() const {
+    // This should only be accessed when jitting.
+    // TODO(johnmccutchan): Remove code back pointer.
+    ASSERT(!Dart::IsRunningPrecompiledCode());
+    return raw_ptr()->code_;
+  }
+
   uword EntryPoint() const {
     return reinterpret_cast<uword>(raw_ptr()) + HeaderSize();
   }
@@ -3752,6 +3759,10 @@ class Instructions : public Object {
     StoreNonPointer(&raw_ptr()->size_, size);
   }
 
+  void set_code(RawCode* code) const {
+    StorePointer(&raw_ptr()->code_, code);
+  }
+
   // New is a private method as RawInstruction and RawCode objects should
   // only be created using the Code::FinalizeCode method. This method creates
   // the RawInstruction and RawCode objects, sets up the pointer offsets