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/jni/jni_compiler_test.cc b/compiler/jni/jni_compiler_test.cc
index 19d55a3..dca290c 100644
--- a/compiler/jni/jni_compiler_test.cc
+++ b/compiler/jni/jni_compiler_test.cc
@@ -1283,7 +1283,7 @@
 
   Thread* self = Thread::Current();
   ScopedObjectAccess soa(self);
-  EXPECT_TRUE(self->HoldsLock(soa.Decode<mirror::Object>(thisObj).Decode()));
+  EXPECT_TRUE(self->HoldsLock(soa.Decode<mirror::Object>(thisObj).Ptr()));
   return nullptr;
 }