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/driver/compiler_driver_test.cc b/compiler/driver/compiler_driver_test.cc
index b924129..e73d072 100644
--- a/compiler/driver/compiler_driver_test.cc
+++ b/compiler/driver/compiler_driver_test.cc
@@ -80,7 +80,7 @@
   void MakeDexFileExecutable(jobject class_loader, const DexFile& dex_file) {
     ClassLinker* class_linker = Runtime::Current()->GetClassLinker();
     for (size_t i = 0; i < dex_file.NumClassDefs(); i++) {
-      const DexFile::ClassDef& class_def = dex_file.GetClassDef(i);
+      const dex::ClassDef& class_def = dex_file.GetClassDef(i);
       const char* descriptor = dex_file.GetClassDescriptor(class_def);
       ScopedObjectAccess soa(Thread::Current());
       StackHandleScope<1> hs(soa.Self());