Improve scroll anchoring's interactions with the visual viewport

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

Index: third_party/WebKit/Source/platform/scroll/ScrollAnimatorCompositorCoordinator.cpp
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollAnimatorCompositorCoordinator.cpp b/third_party/WebKit/Source/platform/scroll/ScrollAnimatorCompositorCoordinator.cpp
index 9c7c007b7642c9c39160f248edfb47a716d5e347..b01312567222d8fa61d42b09b5d8a00715454677 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollAnimatorCompositorCoordinator.cpp
+++ b/third_party/WebKit/Source/platform/scroll/ScrollAnimatorCompositorCoordinator.cpp
@@ -293,11 +293,18 @@ void ScrollAnimatorCompositorCoordinator::updateCompositorAnimations()
     updateImplOnlyCompositorAnimations();
 }
 
+void ScrollAnimatorCompositorCoordinator::scrollPositionChanged(
+    const DoublePoint& offset, ScrollType scrollType)
+{
+    getScrollableArea()->scrollPositionChanged(offset, scrollType);
+}
+
 void ScrollAnimatorCompositorCoordinator::adjustAnimationAndSetScrollPosition(
-    IntSize adjustment, ScrollType scrollType) {
+    const DoublePoint& position, ScrollType scrollType)
+{
     // Subclasses should override this and adjust the animation as necessary.
-    getScrollableArea()->setScrollPosition(
-        getScrollableArea()->scrollPositionDouble() + adjustment, scrollType);
+    DoublePoint adjustedPos = getScrollableArea()->clampScrollPosition(position);
+    scrollPositionChanged(adjustedPos, scrollType);
 }
 
 void ScrollAnimatorCompositorCoordinator::adjustImplOnlyScrollOffsetAnimation(