Replace the bool kDoReadBarrier template parameter with an enum.

Fix one kDoReadBarrier/kIsVolatile mixup in an Object::GetFieldObject
call.

Bug: 12687968

Change-Id: I896b1137b21a20c0504abd2bf3fe6f83805f3300
diff --git a/compiler/image_writer.cc b/compiler/image_writer.cc
index e6d983f..62817e7 100644
--- a/compiler/image_writer.cc
+++ b/compiler/image_writer.cc
@@ -587,7 +587,7 @@
 
   void operator()(Object* obj, MemberOffset offset, bool /*is_static*/) const
       EXCLUSIVE_LOCKS_REQUIRED(Locks::mutator_lock_, Locks::heap_bitmap_lock_) {
-    Object* ref = obj->GetFieldObject<Object, kVerifyNone, false>(offset);
+    Object* ref = obj->GetFieldObject<Object, kVerifyNone>(offset);
     // Use SetFieldObjectWithoutWriteBarrier to avoid card marking since we are writing to the
     // image.
     copy_->SetFieldObjectWithoutWriteBarrier<false, true, kVerifyNone>(