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/optimizing/graph_visualizer.cc b/compiler/optimizing/graph_visualizer.cc
index 0796620..2a7bbcb 100644
--- a/compiler/optimizing/graph_visualizer.cc
+++ b/compiler/optimizing/graph_visualizer.cc
@@ -393,7 +393,7 @@
   void VisitLoadMethodType(HLoadMethodType* load_method_type) override {
     StartAttributeStream("load_kind") << "RuntimeCall";
     const DexFile& dex_file = load_method_type->GetDexFile();
-    const DexFile::ProtoId& proto_id = dex_file.GetProtoId(load_method_type->GetProtoIndex());
+    const dex::ProtoId& proto_id = dex_file.GetProtoId(load_method_type->GetProtoIndex());
     StartAttributeStream("method_type") << dex_file.GetProtoSignature(proto_id);
   }