Use class def index from java.lang.Class.

Bug: 10244719
Depends on:
https://googleplex-android-review.git.corp.google.com/362363
This removes the computation of the dex file index, when necessary this is
computed by searching the dex file. Its only necessary in
dalvik.system.DexFile.defineClassNative and DexFile::FindInClassPath, the
latter not showing up significantly in profiling with this change.

Change-Id: I20c73a3b17d86286428ab0fd21bc13f51f36c85c
diff --git a/compiler/dex/dex_to_dex_compiler.cc b/compiler/dex/dex_to_dex_compiler.cc
index ffd7905..abafbc5 100644
--- a/compiler/dex/dex_to_dex_compiler.cc
+++ b/compiler/dex/dex_to_dex_compiler.cc
@@ -280,7 +280,7 @@
 
 extern "C" void ArtCompileDEX(art::CompilerDriver& compiler, const art::DexFile::CodeItem* code_item,
                   uint32_t access_flags, art::InvokeType invoke_type,
-                  uint32_t class_def_idx, uint32_t method_idx, jobject class_loader,
+                  uint16_t class_def_idx, uint32_t method_idx, jobject class_loader,
                   const art::DexFile& dex_file,
                   art::DexToDexCompilationLevel dex_to_dex_compilation_level) {
   if (dex_to_dex_compilation_level != art::kDontDexToDexCompile) {