Generate scroll/clip display item hierarchy for SPv2

Source/platform/graphics/paint/FixedPositionDisplayItem.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 "platform/graphics/paint/FixedPositionDisplayItem.h"
 
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/transforms/AffineTransform.h"
 #include "public/platform/WebDisplayItemList.h"
 
 namespace blink {
 
 void BeginFixedPositionDisplayItem::appendToWebDisplayItemList(WebDisplayItemList* list) const
 {
-    // TODO(trchen): Should implement the compositor counterpart and update transform tree algorithm.
+    // Note: This is only temporarily workaround before we implement true
+    // transform-tree-based rasterization.
+    AffineTransform transform;
+    transform.translate(m_counterScroll.width(), m_counterScroll.height());
+    list->appendTransformItem(affineTransformToSkMatrix(transform));
 }
 
 void EndFixedPositionDisplayItem::appendToWebDisplayItemList(WebDisplayItemList* list) const
 {
-    // TODO(trchen): Should implement the compositor counterpart and update transform tree algorithm.
+    // Note: This is only temporarily workaround before we implement true
+    // transform-tree-based rasterization.
+    list->appendEndTransformItem();
 }
 
 } // namespace blink