Use ScrollAnchor in FrameView and PaintLayerScrollableArea.

third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp

Index: third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp b/third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp
index 491f7a8af2b8332511ba74428a2479dfd93a63ed..293be128220ead8b02c078a426b7ac4180c1fb90 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp
@@ -287,6 +287,8 @@ void LayoutBlockFlow::layoutBlock(bool relayoutChildren)
 
     LayoutAnalyzer::BlockScope analyzer(*this);
     SubtreeLayoutScope layoutScope(*this);
+    if (scrollAnchoringEnabled() && hasOverflowClip())
+        scrollableArea()->scrollAnchor().save();
 
     // Multiple passes might be required for column based layout.
     // The number of passes could be as high as the number of columns.
@@ -304,6 +306,8 @@ void LayoutBlockFlow::layoutBlock(bool relayoutChildren)
     // Update our scroll information if we're overflow:auto/scroll/hidden now that we know if
     // we overflow or not.
     updateScrollInfoAfterLayout();
+    if (scrollAnchoringEnabled() && hasOverflowClip())
+        scrollableArea()->scrollAnchor().restore();
 
     if (m_paintInvalidationLogicalTop != m_paintInvalidationLogicalBottom) {
         bool hasVisibleContent = style()->visibility() == VISIBLE;