Use float for scroll offset.

third_party/WebKit/Source/core/layout/ScrollAnchor.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 "core/layout/ScrollAnchor.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/UseCounter.h"
 #include "core/layout/LayoutBlockFlow.h"
 #include "core/layout/api/LayoutBoxItem.h"
@@ skipping 94 matching lines @@
   // When root layer scrolling is off, the LayoutView will have no scroll
   // offset (since scrolling is handled by the FrameView) so
   // localToAncestorQuad returns document coords, so we must subtract scroll
   // offset to get viewport coords. We discard the fractional part of the
   // scroll offset so that the rounding in restore() matches the snapping of
   // the anchor node to the pixel grid of the layer it paints into. For
   // non-FrameView scrollers, we rely on the flooring behavior of
   // LayoutBox::scrolledContentOffset.
   if (!RuntimeEnabledFeatures::rootLayerScrollingEnabled() &&
       scrollerBox->isLayoutView())
-    relativeBounds.moveBy(-flooredIntPoint(scroller->scrollPositionDouble()));
+    relativeBounds.moveBy(IntPoint(-scroller->scrollOffsetInt()));
   return relativeBounds;
 }
 
 static LayoutPoint computeRelativeOffset(const LayoutObject* layoutObject,
                                          const ScrollableArea* scroller,
                                          Corner corner) {
   return cornerPointOfRect(relativeBounds(layoutObject, scroller), corner);
 }
 
 static bool candidateMayMoveWithScroller(const LayoutObject* candidate,
@@ skipping 83 matching lines @@
       return false;
     current = current->parent();
   }
 }
 
 void ScrollAnchor::save() {
   if (m_saved)
     return;
   m_saved = true;
   DCHECK(m_scroller);
-
-  ScrollbarOrientation blockLayoutAxis =
+  ScrollOffset scrollOffset = m_scroller->scrollOffset();
+  float blockDirectionScrollOffset =
       scrollerLayoutBox(m_scroller)->isHorizontalWritingMode()
-          ? VerticalScrollbar
-          : HorizontalScrollbar;
-  if (m_scroller->scrollPosition(blockLayoutAxis) == 0) {
+          ? scrollOffset.height()
+          : scrollOffset.width();
+  if (blockDirectionScrollOffset == 0) {
     clear();
     return;
   }
 
   if (!m_anchorObject) {
     findAnchor();
     if (!m_anchorObject)
       return;
 
     m_anchorObject->setIsScrollAnchorObject();
@@ skipping 45 matching lines @@
     // TODO(skobes): add UMA metric for this.
     clear();
 
     DEFINE_STATIC_LOCAL(EnumerationHistogram, suppressedBySanaclapHistogram,
                         ("Layout.ScrollAnchor.SuppressedBySanaclap", 2));
     suppressedBySanaclapHistogram.count(1);
 
     return;
   }
 
-  m_scroller->setScrollPosition(m_scroller->scrollPositionDouble() + adjustment,
-                                AnchoringScroll);
+  m_scroller->setScrollOffset(
+      m_scroller->scrollOffset() + FloatSize(adjustment), AnchoringScroll);
 
   // Update UMA metric.
   DEFINE_STATIC_LOCAL(EnumerationHistogram, adjustedOffsetHistogram,
                       ("Layout.ScrollAnchor.AdjustedScrollOffset", 2));
   adjustedOffsetHistogram.count(1);
   UseCounter::count(scrollerLayoutBox(m_scroller)->document(),
                     UseCounter::ScrollAnchored);
 }
 
 void ScrollAnchor::clear() {
   LayoutObject* anchorObject = m_anchorObject;
   m_anchorObject = nullptr;
 
   if (anchorObject)
     anchorObject->maybeClearIsScrollAnchorObject();
 }
 
 bool ScrollAnchor::refersTo(const LayoutObject* layoutObject) const {
   return m_anchorObject == layoutObject;
 }
 
 void ScrollAnchor::notifyRemoved(LayoutObject* layoutObject) {
   if (m_anchorObject == layoutObject)
     clear();
 }
 
 }  // namespace blink