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/runtime/native/java_lang_Thread.cc b/runtime/native/java_lang_Thread.cc
index 0635261..fcb0175 100644
--- a/runtime/native/java_lang_Thread.cc
+++ b/runtime/native/java_lang_Thread.cc
@@ -116,7 +116,7 @@
   }
   MutexLock mu(soa.Self(), *Locks::thread_list_lock_);
   Thread* thread = Thread::FromManagedThread(soa, java_thread);
-  return thread->HoldsLock(object.Decode());
+  return thread->HoldsLock(object.Ptr());
 }
 
 static void Thread_nativeInterrupt(JNIEnv* env, jobject java_thread) {
@@ -173,7 +173,7 @@
 static void Thread_sleep(JNIEnv* env, jclass, jobject java_lock, jlong ms, jint ns) {
   ScopedFastNativeObjectAccess soa(env);
   ObjPtr<mirror::Object> lock = soa.Decode<mirror::Object>(java_lock);
-  Monitor::Wait(Thread::Current(), lock.Decode(), ms, ns, true, kSleeping);
+  Monitor::Wait(Thread::Current(), lock.Ptr(), ms, ns, true, kSleeping);
 }
 
 /*