[serializer] Ensure immortal immovable roots are deserialized correctly.

src/address-map.cc

Index: src/address-map.cc
diff --git a/src/address-map.cc b/src/address-map.cc
index 681661af2978bbdcc78754a2f9e5a82e1dc9f46d..86558e094aa2215871486d7e1aa656b3d785d2d2 100644
--- a/src/address-map.cc
+++ b/src/address-map.cc
@@ -17,10 +17,10 @@ RootIndexMap::RootIndexMap(Isolate* isolate) {
   for (uint32_t i = 0; i < Heap::kStrongRootListLength; i++) {
     Heap::RootListIndex root_index = static_cast<Heap::RootListIndex>(i);
     Object* root = isolate->heap()->root(root_index);
+    if (!root->IsHeapObject()) continue;
     // Omit root entries that can be written after initialization. They must
     // not be referenced through the root list in the snapshot.
-    if (root->IsHeapObject() &&
-        isolate->heap()->RootCanBeTreatedAsConstant(root_index)) {
+    if (isolate->heap()->RootCanBeTreatedAsConstant(root_index)) {
       HeapObject* heap_object = HeapObject::cast(root);
       HashMap::Entry* entry = LookupEntry(map_, heap_object, false);
       if (entry != NULL) {
@@ -29,6 +29,11 @@ RootIndexMap::RootIndexMap(Isolate* isolate) {
       } else {
         SetValue(LookupEntry(map_, heap_object, true), i);
       }
+    } else {
+      // Immortal immovable root objects are constant and allocated on the first
+      // page of old space. Non-constant roots cannot be immortal immovable. The
+      // root index map contains all immortal immmovable root objects.
+      CHECK(!Heap::RootIsImmortalImmovable(root_index));
     }
   }
   isolate->set_root_index_map(map_);