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/dex_compilation_unit.h b/compiler/driver/dex_compilation_unit.h
index 757f0e7..f68d93f 100644
--- a/compiler/driver/dex_compilation_unit.h
+++ b/compiler/driver/dex_compilation_unit.h
@@ -39,7 +39,7 @@
   DexCompilationUnit(Handle<mirror::ClassLoader> class_loader,
                      ClassLinker* class_linker,
                      const DexFile& dex_file,
-                     const DexFile::CodeItem* code_item,
+                     const dex::CodeItem* code_item,
                      uint16_t class_def_idx,
                      uint32_t method_idx,
                      uint32_t access_flags,
@@ -67,17 +67,17 @@
     return dex_method_idx_;
   }
 
-  const DexFile::CodeItem* GetCodeItem() const {
+  const dex::CodeItem* GetCodeItem() const {
     return code_item_;
   }
 
   const char* GetShorty() const {
-    const DexFile::MethodId& method_id = dex_file_->GetMethodId(dex_method_idx_);
+    const dex::MethodId& method_id = dex_file_->GetMethodId(dex_method_idx_);
     return dex_file_->GetMethodShorty(method_id);
   }
 
   const char* GetShorty(uint32_t* shorty_len) const {
-    const DexFile::MethodId& method_id = dex_file_->GetMethodId(dex_method_idx_);
+    const dex::MethodId& method_id = dex_file_->GetMethodId(dex_method_idx_);
     return dex_file_->GetMethodShorty(method_id, shorty_len);
   }
 
@@ -165,7 +165,7 @@
 
   const DexFile* const dex_file_;
 
-  const DexFile::CodeItem* const code_item_;
+  const dex::CodeItem* const code_item_;
   const uint16_t class_def_idx_;
   const uint32_t dex_method_idx_;
   const uint32_t access_flags_;