Refactor ClassAccessor to use an index instead of ClassDef pointer

Removes a separate class_def_idx being required for getting the index
of a ClassAccessor foreach loop.

Bug: 79758018
Test: test-art-host-gtest

Change-Id: Ie3010a17669f24cf492c678b55bdddba7ec62ea8
diff --git a/compiler/dex/dex_to_dex_decompiler_test.cc b/compiler/dex/dex_to_dex_decompiler_test.cc
index 1fe42ad..d4a9ba5 100644
--- a/compiler/dex/dex_to_dex_decompiler_test.cc
+++ b/compiler/dex/dex_to_dex_decompiler_test.cc
@@ -82,9 +82,8 @@
     ASSERT_NE(0, cmp);
 
     // Unquicken the dex file.
-    for (uint32_t i = 0; i < updated_dex_file->NumClassDefs(); ++i) {
+    for (ClassAccessor accessor : updated_dex_file->GetClasses()) {
       // Unquicken each method.
-      ClassAccessor accessor(*updated_dex_file, updated_dex_file->GetClassDef(i));
       for (const ClassAccessor::Method& method : accessor.GetMethods()) {
         CompiledMethod* compiled_method = compiler_driver_->GetCompiledMethod(
             method.GetReference());