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/oatdump/oatdump.cc b/oatdump/oatdump.cc
index 4d0dc56..a5dc593 100644
--- a/oatdump/oatdump.cc
+++ b/oatdump/oatdump.cc
@@ -1702,7 +1702,7 @@
       mirror::Class* klass = value->AsClass();
       os << StringPrintf("%p   Class: %s\n", klass, PrettyDescriptor(klass).c_str());
     } else {
-      os << StringPrintf("%p   %s\n", value.Decode(), PrettyDescriptor(type).c_str());
+      os << StringPrintf("%p   %s\n", value.Ptr(), PrettyDescriptor(type).c_str());
     }
   }
 
@@ -1748,7 +1748,7 @@
             PrettyObjectValue(os, field_type, value);
           } else {
             os << StringPrintf("%p   %s\n",
-                               value.Decode(),
+                               value.Ptr(),
                                PrettyDescriptor(field->GetTypeDescriptor()).c_str());
           }
         }