Refactor ScrollableArea::setScrollPosition.

third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp

 /*
  * Copyright (c) 2010, Google Inc. All rights reserved.
  * Copyright (C) 2008, 2011 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 160 matching lines @@
   FloatSize unscrollableAxisDelta = pixelDelta - scrollableAxisDelta;
   result.unusedScrollDeltaX += unscrollableAxisDelta.width();
   result.unusedScrollDeltaY += unscrollableAxisDelta.height();
 
   return result;
 }
 
 void ScrollableArea::setScrollPosition(const DoublePoint& position,
                                        ScrollType scrollType,
                                        ScrollBehavior behavior) {
+  DoublePoint clampedPosition = clampScrollPosition(position);
+  if (shouldUseIntegerScrollOffset())
+    clampedPosition = flooredIntPoint(clampedPosition);
+  if (clampedPosition == scrollPositionDouble())
+    return;
+
   if (behavior == ScrollBehaviorAuto)
     behavior = scrollBehaviorStyle();
 
   switch (scrollType) {
     case CompositorScroll:
-      scrollPositionChanged(clampScrollPosition(position), scrollType);
+      scrollPositionChanged(clampedPosition, scrollType);
       break;
     case AnchoringScroll:
-      scrollAnimator().adjustAnimationAndSetScrollPosition(position,
+      scrollAnimator().adjustAnimationAndSetScrollPosition(clampedPosition,
                                                            scrollType);
       break;
     case ProgrammaticScroll:
-      programmaticScrollHelper(position, behavior);
+      programmaticScrollHelper(clampedPosition, behavior);
       break;
     case UserScroll:
-      userScrollHelper(position, behavior);
+      userScrollHelper(clampedPosition, behavior);
       break;
     default:
       ASSERT_NOT_REACHED();
   }
 }
 
 void ScrollableArea::scrollBy(const DoubleSize& delta,
                               ScrollType type,
                               ScrollBehavior behavior) {
   setScrollPosition(scrollPositionDouble() + delta, type, behavior);
@@ skipping 391 matching lines @@
   return IntSize(std::max(0, size.width() - verticalScrollbarWidth()),
                  std::max(0, size.height() - horizontalScrollbarHeight()));
 }
 
 DEFINE_TRACE(ScrollableArea) {
   visitor->trace(m_scrollAnimator);
   visitor->trace(m_programmaticScrollAnimator);
 }
 
 }  // namespace blink