[heap] Only visit strong links during scavenge of promoted objects

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 1cc325bb6501743b6e6be0e2602281ccb1b52c1e..ef7ac6ccc71cbc90234bb1fe432e60ebbd1a901c 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -8562,6 +8562,9 @@ class JSFunction: public JSObject {
   static const int kNextFunctionLinkOffset = kCodeEntryOffset + kPointerSize;
   static const int kSize = kNextFunctionLinkOffset + kPointerSize;
 
+  typedef FixedBodyDescriptor<kNextFunctionLinkOffset, kSize, kSize>
+      BodyDescriptorWeakFields;
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSFunction);
 };