Oilpan: fix build after r189646 (28249fcb).

Source/core/fetch/ResourceFetcherTest.cpp

Index: Source/core/fetch/ResourceFetcherTest.cpp
diff --git a/Source/core/fetch/ResourceFetcherTest.cpp b/Source/core/fetch/ResourceFetcherTest.cpp
index 681f22ca3afe6d6a8f94e1265a3086dfbb7e2707..b2723691e2ecb018b4022ac2316d044e282ff699 100644
--- a/Source/core/fetch/ResourceFetcherTest.cpp
+++ b/Source/core/fetch/ResourceFetcherTest.cpp
@@ -86,7 +86,7 @@ protected:
     // We don't use the DocumentLoader directly in any tests, but need to keep it around as long
     // as the ResourceFetcher and Document live due to indirect usage.
     RefPtr<DocumentLoader> documentLoader;
-    RefPtrWillBeRawPtr<ResourceFetcher> fetcher;
+    RefPtrWillBePersistent<ResourceFetcher> fetcher;
     RefPtrWillBePersistent<Document> document;
 };