Refactor ScrollableArea::setScrollPosition.

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp

Index: third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
index 54d58702ce7aba8c032085c93db3168a3dbf0e41..844ecb8454c83056836308441ef8dd78907f680b 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
@@ -113,10 +113,11 @@ PaintLayerScrollableArea::PaintLayerScrollableArea(PaintLayer& layer)
   if (node && node->isElementNode()) {
     // We save and restore only the scrollOffset as the other scroll values are recalculated.
     Element* element = toElement(node);
-    m_scrollOffset = element->savedLayerScrollOffset();
-    if (!m_scrollOffset.isZero())
+    m_scrollPosition = element->savedLayerScrollOffset();
+    if (!m_scrollPosition.isZero()) {
       scrollAnimator().setCurrentPosition(
-          FloatPoint(m_scrollOffset.width(), m_scrollOffset.height()));
+          FloatPoint(m_scrollPosition.width(), m_scrollPosition.height()));
+    }
     element->setSavedLayerScrollOffset(IntSize());
   }
   updateResizerAreaSet();
@@ -148,9 +149,10 @@ void PaintLayerScrollableArea::dispose() {
   if (!box().documentBeingDestroyed()) {
     Node* node = box().node();
     // FIXME: Make setSavedLayerScrollOffset take DoubleSize. crbug.com/414283.
-    if (node && node->isElementNode())
+    if (node && node->isElementNode()) {
       toElement(node)->setSavedLayerScrollOffset(
-          flooredIntSize(m_scrollOffset));
+          flooredIntSize(m_scrollPosition));
+    }
   }
 
   if (LocalFrame* frame = box().frame()) {
@@ -354,14 +356,14 @@ int PaintLayerScrollableArea::scrollSize(
                                               : scrollDimensions.height();
 }
 
-void PaintLayerScrollableArea::setScrollOffset(
-    const DoublePoint& newScrollOffset,
+void PaintLayerScrollableArea::updateScrollPosition(
+    const DoublePoint& newPosition,
     ScrollType scrollType) {
-  if (scrollOffset() == toDoubleSize(newScrollOffset))
+  if (scrollPositionDouble() == newPosition)
     return;
 
-  DoubleSize scrollDelta = scrollOffset() - toDoubleSize(newScrollOffset);
-  m_scrollOffset = toDoubleSize(newScrollOffset);
+  DoubleSize scrollDelta = scrollPositionDouble() - newPosition;
+  m_scrollPosition = toDoubleSize(newPosition);
 
   LocalFrame* frame = box().frame();
   ASSERT(frame);
@@ -455,11 +457,11 @@ void PaintLayerScrollableArea::setScrollOffset(
 }
 
 IntPoint PaintLayerScrollableArea::scrollPosition() const {
-  return IntPoint(flooredIntSize(m_scrollOffset));
+  return IntPoint(flooredIntSize(m_scrollPosition));
 }
 
 DoublePoint PaintLayerScrollableArea::scrollPositionDouble() const {
-  return DoublePoint(m_scrollOffset);
+  return DoublePoint(m_scrollPosition);
 }
 
 IntPoint PaintLayerScrollableArea::minimumScrollPosition() const {
@@ -498,8 +500,9 @@ IntRect PaintLayerScrollableArea::visibleContentRect(
             : 0;
   }
 
+  // TODO(szager): Handle fractional scroll offsets correctly.
   return IntRect(
-      IntPoint(scrollXOffset(), scrollYOffset()),
+      IntPoint(flooredIntSize(offsetFromOrigin())),
       IntSize(max(0, layer()->size().width() - verticalScrollbarWidth),
               max(0, layer()->size().height() - horizontalScrollbarHeight)));
 }
@@ -635,17 +638,11 @@ void PaintLayerScrollableArea::updateScrollDimensions() {
   updateScrollOrigin();
 }
 
-void PaintLayerScrollableArea::scrollToPosition(
-    const DoublePoint& scrollPosition,
-    ScrollOffsetClamping clamp,
-    ScrollBehavior scrollBehavior,
+void PaintLayerScrollableArea::setScrollPositionUnconditionally(
+    const DoublePoint& position,
     ScrollType scrollType) {
-  DoublePoint newScrollPosition = clamp == ScrollOffsetClamped
-                                      ? clampScrollPosition(scrollPosition)
-                                      : scrollPosition;
-  if (newScrollPosition != scrollPositionDouble())
-    ScrollableArea::setScrollPosition(newScrollPosition, scrollType,
-                                      scrollBehavior);
+  cancelScrollAnimation();
+  scrollPositionChanged(position, scrollType);
 }
 
 void PaintLayerScrollableArea::updateAfterLayout() {
@@ -807,7 +804,9 @@ void PaintLayerScrollableArea::clampScrollPositionsAfterLayout() {
     m_scrollAnchor.restore();
 
   DoublePoint clamped = clampScrollPosition(scrollPositionDouble());
-  if (clamped != scrollPositionDouble() || scrollOriginChanged())
+  if (scrollOriginChanged())
+    setScrollPositionUnconditionally(clamped);
+  else if (clamped != scrollPositionDouble())
     ScrollableArea::setScrollPosition(clamped, ProgrammaticScroll);
 
   setNeedsScrollPositionClamp(false);
@@ -1560,9 +1559,10 @@ LayoutRect PaintLayerScrollableArea::scrollIntoView(
   LayoutRect r = ScrollAlignment::getRectToExpose(layerBounds, localExposeRect,
                                                   alignX, alignY);
 
-  DoublePoint clampedScrollPosition = clampScrollPosition(
-      scrollPositionDouble() + roundedIntSize(r.location()));
-  if (clampedScrollPosition == scrollPositionDouble())
+  DoublePoint oldScrollPosition = scrollPositionDouble();
+  DoublePoint newScrollPosition =
+      clampScrollPosition(oldScrollPosition + roundedIntSize(r.location()));
+  if (newScrollPosition == oldScrollPosition)
     return LayoutRect(
         box()
             .localToAbsoluteQuad(FloatQuad(FloatRect(intersection(
@@ -1570,10 +1570,9 @@ LayoutRect PaintLayerScrollableArea::scrollIntoView(
                                  UseTransforms)
             .boundingBox());
 
-  DoubleSize oldScrollOffset = adjustedScrollOffset();
-  scrollToPosition(clampedScrollPosition, ScrollOffsetUnclamped,
-                   ScrollBehaviorInstant, scrollType);
-  DoubleSize scrollOffsetDifference = adjustedScrollOffset() - oldScrollOffset;
+  setScrollPosition(newScrollPosition, scrollType, ScrollBehaviorInstant);
+  DoubleSize scrollOffsetDifference =
+      scrollPositionDouble() - oldScrollPosition;
   localExposeRect.move(-LayoutSize(scrollOffsetDifference));
   return LayoutRect(
       box()