[cleanup] Don't crash when printing context->previous()

Bug: v8:8834
Change-Id: I5730e550f1b19e651d1fa7cb8b5694c9d839ff84
Reviewed-on: https://chromium-review.googlesource.com/c/1480374Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59763}

src/contexts-inl.h

@@ -77,6 +77,8 @@ void Context::set_scope_info(ScopeInfo scope_info) {
   set(SCOPE_INFO_INDEX, scope_info);
 }
 
+Object Context::unchecked_previous() { return get(PREVIOUS_INDEX); }
+
 Context Context::previous() {
   Object result = get(PREVIOUS_INDEX);
   DCHECK(IsBootstrappingOrValidParentContext(result, *this));

src/contexts.h

@@ -538,6 +538,8 @@ class Context : public HeapObject {
 
   // Direct slot access.
   inline void set_scope_info(ScopeInfo scope_info);
+
+  inline Object unchecked_previous();
   inline Context previous();
   inline void set_previous(Context context);
 

src/objects-printer.cc

@@ -958,7 +958,7 @@ void PrintContextWithHeader(std::ostream& os, Context context,
   context->PrintHeader(os, type);
   os << "\n - length: " << context->length();
   os << "\n - scope_info: " << Brief(context->scope_info());
-  os << "\n - previous: " << Brief(context->previous());
+  os << "\n - previous: " << Brief(context->unchecked_previous());
   os << "\n - extension: " << Brief(context->extension());
   os << "\n - native_context: " << Brief(context->native_context());
   PrintFixedArrayElements(os, context);