Oilpan: Remove most WillBe types from the code base

third_party/WebKit/Source/modules/csspaint/PaintWorklet.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef PaintWorklet_h
 #define PaintWorklet_h
 
 #include "modules/worklet/Worklet.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
 class PaintWorklet final : public Worklet {
     WTF_MAKE_NONCOPYABLE(PaintWorklet);
 public:
     static PaintWorklet* create(LocalFrame*, ExecutionContext*);
     ~PaintWorklet() override;
 
     WorkletGlobalScope* workletGlobalScope() const final { return m_paintWorkletGlobalScope.get(); }
 
     DECLARE_VIRTUAL_TRACE();
 
 private:
     PaintWorklet(LocalFrame*, ExecutionContext*);
 
-    RefPtrWillBeMember<WorkletGlobalScope> m_paintWorkletGlobalScope;
+    Member<WorkletGlobalScope> m_paintWorkletGlobalScope;
 };
 
 } // namespace blink
 
 #endif // PaintWorklet_h