Have ResizeViewportAnchor derive from GarbageCollected<> only.

third_party/WebKit/Source/web/ResizeViewportAnchor.cpp

 // 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.
 
 #include "web/ResizeViewportAnchor.h"
 
 #include "core/frame/FrameHost.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/VisualViewport.h"
 #include "core/page/Page.h"
 #include "platform/geometry/DoubleRect.h"
-#include "platform/geometry/DoubleSize.h"
 #include "platform/geometry/FloatSize.h"
 
 namespace blink {
 
 void ResizeViewportAnchor::resizeFrameView(IntSize size)
 {
     FrameView* frameView = rootFrameView();
     DCHECK(frameView);
 
     ScrollableArea* rootViewport = frameView->getScrollableArea();
@@ skipping 64 matching lines @@
 FrameView* ResizeViewportAnchor::rootFrameView()
 {
     if (Frame* frame = m_page->mainFrame()) {
         if (frame->isLocalFrame())
             return toLocalFrame(frame)->view();
     }
     return nullptr;
 }
 
 } // namespace blink