Oilpan: have xml/ objects on the heap by default.

Source/core/inspector/InspectorDOMAgent.cpp

 /*
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Google Inc. All rights reserved.
  * Copyright (C) 2009 Joseph Pecoraro
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
@@ skipping 1055 matching lines @@
             }
             default:
                 break;
             }
         }
 
         // XPath evaluation
         for (Document* document : docs) {
             ASSERT(document);
             TrackExceptionState exceptionState;
-            RefPtrWillBeRawPtr<XPathResult> result = DocumentXPathEvaluator::evaluate(*document, whitespaceTrimmedQuery, document, nullptr, XPathResult::ORDERED_NODE_SNAPSHOT_TYPE, ScriptValue(), exceptionState);
+            XPathResult* result = DocumentXPathEvaluator::evaluate(*document, whitespaceTrimmedQuery, document, nullptr, XPathResult::ORDERED_NODE_SNAPSHOT_TYPE, ScriptValue(), exceptionState);
             if (exceptionState.hadException() || !result)
                 continue;
 
             unsigned long size = result->snapshotLength(exceptionState);
             for (unsigned long i = 0; !exceptionState.hadException() && i < size; ++i) {
                 Node* node = result->snapshotItem(i, exceptionState);
                 if (exceptionState.hadException())
                     break;
 
                 if (node->nodeType() == Node::ATTRIBUTE_NODE)
@@ skipping 1149 matching lines @@
     visitor->trace(m_searchResults);
 #endif
     visitor->trace(m_hoveredNodeForInspectMode);
     visitor->trace(m_history);
     visitor->trace(m_domEditor);
     visitor->trace(m_listener);
     InspectorBaseAgent::trace(visitor);
 }
 
 } // namespace blink