Fix code flusher to process weak function links.

src/mark-compact.h

Index: src/mark-compact.h
diff --git a/src/mark-compact.h b/src/mark-compact.h
index 7ab83c41e56a0f392ca68bf5b8ea1ec4507ec652..8b1620eb21baf51c5a0f78756dc807ad5b84a21d 100644
--- a/src/mark-compact.h
+++ b/src/mark-compact.h
@@ -441,10 +441,17 @@ class CodeFlusher {
     ProcessJSFunctionCandidates();
   }
 
+  void IteratePointersToFromSpace(ObjectVisitor* v);
+
  private:
   void ProcessJSFunctionCandidates();
   void ProcessSharedFunctionInfoCandidates();
 
+  static JSFunction** GetNextCandidateSlot(JSFunction* candidate) {
+    return reinterpret_cast<JSFunction**>(
+        HeapObject::RawField(candidate, JSFunction::kNextFunctionLinkOffset));
+  }
+
   static JSFunction* GetNextCandidate(JSFunction* candidate) {
     Object* next_candidate = candidate->next_function_link();
     return reinterpret_cast<JSFunction*>(next_candidate);