Revert of Remove invert viewport scroll order setting from Blink

third_party/WebKit/Source/core/frame/RootFrameViewport.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 "config.h"
 #include "core/frame/RootFrameViewport.h"
 
 #include "core/frame/FrameView.h"
 #include "core/layout/ScrollAlignment.h"
 #include "platform/geometry/DoubleRect.h"
 #include "platform/geometry/FloatRect.h"
 #include "platform/geometry/LayoutRect.h"
 
 namespace blink {
 
-RootFrameViewport::RootFrameViewport(ScrollableArea& visualViewport, ScrollableArea& layoutViewport)
+RootFrameViewport::RootFrameViewport(ScrollableArea& visualViewport, ScrollableArea& layoutViewport, bool invertScrollOrder)
     : m_visualViewport(visualViewport)
     , m_layoutViewport(layoutViewport)
+    , m_invertScrollOrder(invertScrollOrder)
 {
 }
 
 void RootFrameViewport::updateScrollAnimator()
 {
     scrollAnimator()->setCurrentPosition(toFloatPoint(scrollOffsetFromScrollAnimators()));
 }
 
 DoublePoint RootFrameViewport::scrollOffsetFromScrollAnimators() const
 {
@@ skipping 104 matching lines @@
 {
     // Make sure we use the scroll positions as reported by each viewport's ScrollAnimatorBase, since its
     // ScrollableArea's position may have the fractional part truncated off.
     DoublePoint oldPosition = scrollOffsetFromScrollAnimators();
 
     DoubleSize delta = offset - oldPosition;
 
     if (delta.isZero())
         return;
 
-    DoublePoint targetPosition = visualViewport().clampScrollPosition(
-        visualViewport().scrollAnimator()->currentPosition() + delta);
+    ScrollableArea& primary = !m_invertScrollOrder ? layoutViewport() : visualViewport();
+    ScrollableArea& secondary = !m_invertScrollOrder ? visualViewport() : layoutViewport();
 
-    visualViewport().setScrollPosition(targetPosition, scrollType, behavior);
+    DoublePoint targetPosition = primary.clampScrollPosition(primary.scrollAnimator()->currentPosition() + delta);
+    primary.setScrollPosition(targetPosition, scrollType, behavior);
 
-    // Scroll the layout viewport if all of the scroll was not applied to the
-    // visual viewport.
-    DoublePoint updatedPosition = layoutViewport().scrollAnimator()->currentPosition() + FloatPoint(targetPosition);
+    // Scroll the secondary viewport if all of the scroll was not applied to the
+    // primary viewport.
+    DoublePoint updatedPosition = secondary.scrollAnimator()->currentPosition() + FloatPoint(targetPosition);
     DoubleSize applied = updatedPosition - oldPosition;
     delta -= applied;
 
     if (delta.isZero())
         return;
 
-    targetPosition = layoutViewport().clampScrollPosition(layoutViewport().scrollAnimator()->currentPosition() + delta);
-    layoutViewport().setScrollPosition(targetPosition, scrollType, behavior);
+    targetPosition = secondary.clampScrollPosition(secondary.scrollAnimator()->currentPosition() + delta);
+    secondary.setScrollPosition(targetPosition, scrollType, behavior);
 }
 
 IntPoint RootFrameViewport::scrollPosition() const
 {
     return flooredIntPoint(scrollPositionDouble());
 }
 
 DoublePoint RootFrameViewport::scrollPositionDouble() const
 {
     return layoutViewport().scrollPositionDouble() + toDoubleSize(visualViewport().scrollPositionDouble());
@@ skipping 112 matching lines @@
 }
 
 DEFINE_TRACE(RootFrameViewport)
 {
     visitor->trace(m_visualViewport);
     visitor->trace(m_layoutViewport);
     ScrollableArea::trace(visitor);
 }
 
 } // namespace blink