Clean up AtomicDexRefMap

Make ClassReference, TypeReference, and MethodReference extend
DexFileReference. This enables using all of these types as the key
for AtomicDexRefMap.

Test: test-art-host
Bug: 63851220
Bug: 63756964

Change-Id: Ida3c94cadb53272cb5057e5cebc5971c1ab4d366
diff --git a/compiler/dex/inline_method_analyser.cc b/compiler/dex/inline_method_analyser.cc
index 54ddc21..c8e3d5e 100644
--- a/compiler/dex/inline_method_analyser.cc
+++ b/compiler/dex/inline_method_analyser.cc
@@ -509,7 +509,7 @@
 }
 
 bool InlineMethodAnalyser::IsSyntheticAccessor(MethodReference ref) {
-  const DexFile::MethodId& method_id = ref.dex_file->GetMethodId(ref.dex_method_index);
+  const DexFile::MethodId& method_id = ref.dex_file->GetMethodId(ref.index);
   const char* method_name = ref.dex_file->GetMethodName(method_id);
   // javac names synthetic accessors "access$nnn",
   // jack names them "-getN", "-putN", "-wrapN".