Fixed pos objects are offset from the top of the page in paged media

third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp

Index: third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp b/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
index 266f59d3bdc26fbf1519e946160ada2a2d408336..90284da8bac156f154059e8e085813d3bcf70e4d 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
@@ -586,6 +586,12 @@ PaintLayerPainter::PaintResult PaintLayerPainter::paintLayerWithTransform(
     unsigned pages =
         ceilf(view->documentRect().height() / view->pageLogicalHeight());
     LayoutPoint paginationOffset;
+
+    // The fixed position object is offset from the top of the page, so remove any scroll offset.

[Xianzhu, 2016/10/06 22:40:42]

Nit: Wrap at 80 chars. (Though there are other comments exceeding 80 chars, some
ones may be working on fixing them, so we should not introduce new ones.)

+    LayoutPoint offsetFromRoot;
+    m_paintLayer.convertToLayerCoords(paintingInfo.rootLayer, offsetFromRoot);
+    paginationOffset -= offsetFromRoot - m_paintLayer.location();
+
     for (unsigned i = 0; i < pages; i++) {
       PaintLayerFragment fragment;
       fragment.backgroundRect = paintingInfo.paintDirtyRect;