WIP (Introduce WTF::NonNullPtr<T>.)

Source/core/page/Frame.h

Index: Source/core/page/Frame.h
diff --git a/Source/core/page/Frame.h b/Source/core/page/Frame.h
index 1a912eb6c1f80af8cf15e7f727852f7dd4cf6742..625fd05fe2d7f741a391dfda05d04b3240f35f83 100644
--- a/Source/core/page/Frame.h
+++ b/Source/core/page/Frame.h
@@ -35,6 +35,7 @@
 #include "core/platform/ScrollTypes.h"
 #include "core/platform/graphics/IntSize.h"
 #include "wtf/Forward.h"
+#include "wtf/NonNullPtr.h"
 #include "wtf/RefCounted.h"
 
 namespace WebCore {
@@ -100,7 +101,7 @@ namespace WebCore {
         NavigationScheduler* navigationScheduler() const;
         FrameSelection& selection() const;
         FrameTree* tree() const;
-        AnimationController* animation() const;
+        NonNullPtr<AnimationController> animation() const;
         InputMethodController& inputMethodController() const;
         FetchContext& fetchContext() const { return loader()->fetchContext(); }
         ScriptController* script();
@@ -241,7 +242,7 @@ namespace WebCore {
         return *m_editor;
     }
 
-    inline AnimationController* Frame::animation() const
+    inline NonNullPtr<AnimationController> Frame::animation() const
     {
         return m_animationController.get();
     }