Oilpan: Fix compile after r199777.

Source/modules/webusb/USBController.h

 // Copyright 2015 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 USBController_h
 #define USBController_h
 
 #include "core/frame/LocalFrame.h"
 #include "core/frame/LocalFrameLifecycleObserver.h"
 #include "modules/ModulesExport.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
 class WebUSBClient;
 
 class MODULES_EXPORT USBController final
     : public NoBaseWillBeGarbageCollectedFinalized<USBController>
     , public WillBeHeapSupplement<LocalFrame>
     , public LocalFrameLifecycleObserver {
     WTF_MAKE_NONCOPYABLE(USBController);
+    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(USBController);
 public:
     virtual ~USBController();
 
     WebUSBClient* client() { return m_client; }
 
     static void provideTo(LocalFrame&, WebUSBClient*);
     static USBController& from(LocalFrame&);
     static const char* supplementName();
 
     DECLARE_VIRTUAL_TRACE();
 
 private:
     USBController(LocalFrame&, WebUSBClient*);
 
     // Inherited from LocalFrameLifecycleObserver.
     void willDetachFrameHost() override;
 
     WebUSBClient* m_client;
 };
 
 } // namespace blink
 
 #endif // USBController_h