ART: Move dex structs into own header

Separating out the structs from DexFile allows them to be forward-
declared, which reduces the need to include the dex_file header.

Bug: 119869270
Test: m
Change-Id: I32dde5a632884bca7435cd584b4a81883de2e7b4
diff --git a/compiler/debug/elf_debug_writer.cc b/compiler/debug/elf_debug_writer.cc
index 0f2d73e..16f163b 100644
--- a/compiler/debug/elf_debug_writer.cc
+++ b/compiler/debug/elf_debug_writer.cc
@@ -54,7 +54,7 @@
   WriteCFISection(builder, debug_info.compiled_methods, cfi_format, write_oat_patches);
 
   // Group the methods into compilation units based on class.
-  std::unordered_map<const DexFile::ClassDef*, ElfCompilationUnit> class_to_compilation_unit;
+  std::unordered_map<const dex::ClassDef*, ElfCompilationUnit> class_to_compilation_unit;
   for (const MethodDebugInfo& mi : debug_info.compiled_methods) {
     if (mi.dex_file != nullptr) {
       auto& dex_class_def = mi.dex_file->GetClassDef(mi.class_def_index);