[heap] All immutable roots are either smis or immovable heap objects.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index bc46cc2cff46d51d2ebaed81bce29d7476d25560..8fb72dc6d9b45b9b82cd92db61873ba0524635f0 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -3316,8 +3316,11 @@ bool Heap::RootCanBeWrittenAfterInitialization(Heap::RootListIndex root_index) {
 
 
 bool Heap::RootCanBeTreatedAsConstant(RootListIndex root_index) {
-  return !RootCanBeWrittenAfterInitialization(root_index) &&
-         !InNewSpace(roots_array_start()[root_index]);
+  if (!RootCanBeWrittenAfterInitialization(root_index)) {
+    DCHECK(!InNewSpace(roots_array_start()[root_index]));
+    return true;
+  }
+  return false;
 }