Use float for scroll offset.

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/RootFrameViewport.h"
 #include "core/frame/VisualViewport.h"
 #include "core/page/Page.h"
 #include "platform/geometry/DoubleRect.h"
 #include "platform/geometry/FloatSize.h"
 
 namespace blink {
 
 void ResizeViewportAnchor::resizeFrameView(IntSize size) {
   FrameView* frameView = rootFrameView();
   DCHECK(frameView);
 
   ScrollableArea* rootViewport = frameView->getScrollableArea();
-  DoublePoint position = rootViewport->scrollPositionDouble();
+  ScrollOffset offset = rootViewport->scrollOffset();
 
   frameView->resize(size);
-  m_drift += rootViewport->scrollPositionDouble() - position;
+  m_drift += rootViewport->scrollOffset() - offset;
 }
 
 void ResizeViewportAnchor::endScope() {
   if (--m_scopeCount > 0)
     return;
 
   FrameView* frameView = rootFrameView();
   if (!frameView)
     return;
 
-  DoublePoint visualViewportInDocument =
-      frameView->getScrollableArea()->scrollPositionDouble() - m_drift;
+  ScrollOffset visualViewportInDocument =
+      frameView->getScrollableArea()->scrollOffset() - m_drift;
 
   // TODO(bokan): Don't use RootFrameViewport::setScrollPosition since it
   // assumes we can just set a sub-pixel precision offset on the FrameView.
   // While we "can" do this, the offset that will be shipped to CC will be the
   // truncated number and this class is used to handle TopControl movement
   // which needs the two threads to match exactly pixel-for-pixel. We can
   // replace this with RFV::setScrollPosition once Blink is sub-pixel scroll
   // offset aware. crbug.com/414283.
   DCHECK(frameView->getRootFrameViewport());
   frameView->getRootFrameViewport()->restoreToAnchor(visualViewportInDocument);
 
-  m_drift = DoubleSize();
+  m_drift = ScrollOffset();
 }
 
 FrameView* ResizeViewportAnchor::rootFrameView() {
   if (Frame* frame = m_page->mainFrame()) {
     if (frame->isLocalFrame())
       return toLocalFrame(frame)->view();
   }
   return nullptr;
 }
 
 }  // namespace blink