[lldb][DWARFASTParserClang] GetCXXObjectParameter to take DeclContext DIE parameter (#144876)

I'm trying to call `GetCXXObjectParameter` from unit-tests in a
follow-up patch and taking a `DWARFDIE` instead of `clang::DeclContext`
makes that much simpler. These should be equivalent, since all we're
trying to check is that the parent context is a record type.

Author: Michael137

lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp

@@ -163,14 +163,14 @@ static bool TagIsRecordType(dw_tag_t tag) {
 /// a default DWARFDIE. If \c containing_decl_ctx is not a valid
 /// C++ declaration context for class methods, assume no object
 /// parameter exists for the given \c subprogram.
-static DWARFDIE
-GetCXXObjectParameter(const DWARFDIE &subprogram,
-                      const clang::DeclContext &containing_decl_ctx) {
+static DWARFDIE GetCXXObjectParameter(const DWARFDIE &subprogram,
+                                      const DWARFDIE &decl_ctx_die) {
+  assert(subprogram);
   assert(subprogram.Tag() == DW_TAG_subprogram ||
          subprogram.Tag() == DW_TAG_inlined_subroutine ||
          subprogram.Tag() == DW_TAG_subroutine_type);
 
-  if (!DeclKindIsCXXClass(containing_decl_ctx.getDeclKind()))
+  if (!decl_ctx_die.IsStructUnionOrClass())
     return {};
 
   if (DWARFDIE object_parameter =
@@ -1304,8 +1304,7 @@ DWARFASTParserClang::ParseSubroutine(const DWARFDIE &die,
   clang::CallingConv calling_convention =
       ConvertDWARFCallingConventionToClang(attrs);
 
-  const DWARFDIE object_parameter =
-      GetCXXObjectParameter(die, *containing_decl_ctx);
+  const DWARFDIE object_parameter = GetCXXObjectParameter(die, decl_ctx_die);
 
   // clang_type will get the function prototype clang type after this
   // call
@@ -2411,12 +2410,13 @@ DWARFASTParserClang::ConstructDemangledNameFromDWARF(const DWARFDIE &die) {
   DWARFDeclContext decl_ctx = die.GetDWARFDeclContext();
   sstr << decl_ctx.GetQualifiedName();
 
+  DWARFDIE decl_ctx_die;
   clang::DeclContext *containing_decl_ctx =
-      GetClangDeclContextContainingDIE(die, nullptr);
+      GetClangDeclContextContainingDIE(die, &decl_ctx_die);
   assert(containing_decl_ctx);
 
-  const unsigned cv_quals = GetCXXMethodCVQuals(
-      die, GetCXXObjectParameter(die, *containing_decl_ctx));
+  const unsigned cv_quals =
+      GetCXXMethodCVQuals(die, GetCXXObjectParameter(die, decl_ctx_die));
 
   ParseChildParameters(containing_decl_ctx, die, is_variadic,
                        has_template_params, param_types, param_names);