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/mir_graph.cc b/compiler/dex/mir_graph.cc
index c72283e..c234298 100644
--- a/compiler/dex/mir_graph.cc
+++ b/compiler/dex/mir_graph.cc
@@ -504,7 +504,7 @@
 
 /* Parse a Dex method and insert it into the MIRGraph at the current insert point. */
 void MIRGraph::InlineMethod(const DexFile::CodeItem* code_item, uint32_t access_flags,
-                           InvokeType invoke_type, uint32_t class_def_idx,
+                           InvokeType invoke_type, uint16_t class_def_idx,
                            uint32_t method_idx, jobject class_loader, const DexFile& dex_file) {
   current_code_item_ = code_item;
   method_stack_.push_back(std::make_pair(current_method_, current_offset_));