Oilpan: Remove most WillBe types from the code base

third_party/WebKit/Source/core/streams/UnderlyingSourceBase.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 UnderlyingSourceBase_h
 #define UnderlyingSourceBase_h
 
 #include "bindings/core/v8/ActiveScriptWrappable.h"
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptState.h"
 #include "bindings/core/v8/ScriptValue.h"
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/CoreExport.h"
 #include "core/dom/ActiveDOMObject.h"
 #include "platform/heap/GarbageCollected.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
 class ReadableStreamController;
 
 class CORE_EXPORT UnderlyingSourceBase : public GarbageCollectedFinalized<UnderlyingSourceBase>, public ScriptWrappable, public ActiveScriptWrappable, public ActiveDOMObject {
     DEFINE_WRAPPERTYPEINFO();
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(UnderlyingSourceBase);
+    USING_GARBAGE_COLLECTED_MIXIN(UnderlyingSourceBase);
 
 public:
     DECLARE_VIRTUAL_TRACE();
     virtual ~UnderlyingSourceBase() {}
 
     ScriptPromise startWrapper(ScriptState*, ScriptValue stream);
     virtual ScriptPromise start(ScriptState*);
 
     virtual ScriptPromise pull(ScriptState*);
 
@@ skipping 16 matching lines @@
 
     ReadableStreamController* controller() const { return m_controller; }
 
 private:
     Member<ReadableStreamController> m_controller;
 };
 
 } // namespace blink
 
 #endif // UnderlyingSourceBase_h