Rename ObjPtr::Decode to ObjPtr::Ptr

Done to prevent ambiguity with ScopedObjectAccess::Decode.

Bug: 31113334

Test: test-art-host
Change-Id: I07a2497cc9cf66386311798933547471987fc316
diff --git a/compiler/oat_test.cc b/compiler/oat_test.cc
index e8bc67d..9f352ce 100644
--- a/compiler/oat_test.cc
+++ b/compiler/oat_test.cc
@@ -498,7 +498,7 @@
   for (const DexFile* dex_file : dex_files) {
     ScopedObjectAccess soa(Thread::Current());
     class_linker->RegisterDexFile(*dex_file,
-                                  soa.Decode<mirror::ClassLoader>(class_loader).Decode());
+                                  soa.Decode<mirror::ClassLoader>(class_loader).Ptr());
   }
   compiler_driver_->SetDexFilesForOatFile(dex_files);
   compiler_driver_->CompileAll(class_loader, dex_files, &timings);