[vm] Fix assert in heap snapshot writer.

TEST=iso-stress
Bug: #60701
Change-Id: I0e66fc1e9ce38eb566f68eddb63ebbe5e2200275
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/428081
Commit-Queue: Ryan Macnak <[email protected]>
Reviewed-by: Alexander Aprelev <[email protected]>

Author: rmacnak-google

runtime/vm/object_graph.cc

@@ -131,10 +131,10 @@ class ObjectSlots {
       // and be without holes (otherwise, e.g. if a slot was not declared,
       // the visitors will visit them but we won't emit the field description in
       // the heap snapshot).
-      if (contains_only_tagged_words) {
-        intptr_t expected_offset = kWordSize;
+      if (contains_only_tagged_words && (slots->length() > 0)) {
+        intptr_t expected_offset = (*slots)[0].offset;
         for (auto& slot : *slots) {
-          RELEASE_ASSERT(slot.offset = expected_offset);
+          ASSERT_EQUAL(slot.offset, expected_offset);
           expected_offset += kCompressedWordSize;
         }
       }

runtime/vm/raw_object_fields.cc

@@ -28,6 +28,7 @@ namespace dart {
   F(Class, constants_)                                                         \
   F(Class, declaration_type_)                                                  \
   F(Class, invocation_dispatcher_cache_)                                       \
+  F(Class, declaration_instance_type_arguments_)                               \
   F(PatchClass, wrapped_class_)                                                \
   F(PatchClass, script_)                                                       \
   F(Function, name_)                                                           \
@@ -246,10 +247,11 @@ namespace dart {
   F(Class, direct_subclasses_)
 
 #define JIT_CLASSES_AND_FIELDS(F)                                              \
-  F(Class, allocation_stub_)                                                   \
-  F(Class, dependent_code_)                                                    \
   F(Class, direct_implementors_)                                               \
   F(Class, direct_subclasses_)                                                 \
+  F(Class, allocation_stub_)                                                   \
+  F(Class, dependent_code_)                                                    \
+  F(Library, kernel_program_info_)                                             \
   F(Code, active_instructions_)                                                \
   F(Code, deopt_info_array_)                                                   \
   F(Code, static_calls_target_table_)                                          \