Oilpan: Remove most WillBe types from the code base

third_party/WebKit/Source/core/animation/AnimationStackTest.cpp

Index: third_party/WebKit/Source/core/animation/AnimationStackTest.cpp
diff --git a/third_party/WebKit/Source/core/animation/AnimationStackTest.cpp b/third_party/WebKit/Source/core/animation/AnimationStackTest.cpp
index 95df90666a3f9be70ff652b2ff957037a15b2426..5b91f0ca723c9adc98eae08b3745e2f996868d94 100644
--- a/third_party/WebKit/Source/core/animation/AnimationStackTest.cpp
+++ b/third_party/WebKit/Source/core/animation/AnimationStackTest.cpp
@@ -79,9 +79,9 @@ protected:
     }
 
     OwnPtr<DummyPageHolder> pageHolder;
-    RefPtrWillBePersistent<Document> document;
+    Persistent<Document> document;
     Persistent<AnimationTimeline> timeline;
-    RefPtrWillBePersistent<Element> element;
+    Persistent<Element> element;
 };
 
 TEST_F(AnimationAnimationStackTest, ElementAnimationsSorted)