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

Source/bindings/core/v8/custom/V8CustomXPathNSResolver.h

Index: Source/bindings/core/v8/custom/V8CustomXPathNSResolver.h
diff --git a/Source/bindings/core/v8/custom/V8CustomXPathNSResolver.h b/Source/bindings/core/v8/custom/V8CustomXPathNSResolver.h
index 8ffe5546251924078ef36e776cb4fd1e7b30d724..778702db54138ab798602fe28fbc33770cc6d673 100644
--- a/Source/bindings/core/v8/custom/V8CustomXPathNSResolver.h
+++ b/Source/bindings/core/v8/custom/V8CustomXPathNSResolver.h
@@ -45,7 +45,7 @@ namespace blink {
 // must not exceed the lifetime of the passed handle.
 class V8CustomXPathNSResolver final : public XPathNSResolver {
 public:
-    static PassRefPtrWillBeRawPtr<V8CustomXPathNSResolver> create(ScriptState*, v8::Local<v8::Object> resolver);
+    static V8CustomXPathNSResolver* create(ScriptState*, v8::Local<v8::Object> resolver);
 
     virtual AtomicString lookupNamespaceURI(const String& prefix) override;