Only adjust composited pagination position to account for lines offset of inlines.

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp

Index: third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
diff --git a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
index b938ccffbe207cb53c29ea507fcb973da2d904a8..3cc9f55079373cb20da029a5340113d05db1564a 100644
--- a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
@@ -41,6 +41,7 @@
 #include "core/layout/LayoutEmbeddedObject.h"
 #include "core/layout/LayoutHTMLCanvas.h"
 #include "core/layout/LayoutImage.h"
+#include "core/layout/LayoutInline.h"
 #include "core/layout/LayoutPart.h"
 #include "core/layout/LayoutVideo.h"
 #include "core/layout/LayoutView.h"
@@ -884,10 +885,17 @@ void CompositedLayerMapping::ComputeBoundsOfOwningLayer(
     IntRect& compositing_bounds_relative_to_composited_ancestor,
     LayoutPoint& offset_from_composited_ancestor,
     IntPoint& snapped_offset_from_composited_ancestor) {
-  LayoutRect local_raw_compositing_bounds = CompositedBounds();
+  // HACK(chrishtr): adjust for position of inlines.
+  LayoutPoint local_representative_point_for_fragmentation;
+  if (owning_layer_.GetLayoutObject().IsLayoutInline()) {
+    local_representative_point_for_fragmentation =
+        ToLayoutInline(owning_layer_.GetLayoutObject())
+            .LinesVisualOverflowBoundingBox()

[trchen, 2017/05/16 23:26:47]

LinesVisualOverflowBoundingBox can be expensive (have to collect all descendant
line boxes.). And I'm not sure we actually want to include visual overflow, as
say, wouldn't top-left box shadow cause the same issue?

How about .FirstLineBoxTopLeft() ? Feels like exactly what we want.

[chrishtr, 2017/05/17 02:00:14]

Done, good idea.

+            .Location();
+  }
   offset_from_composited_ancestor = ComputeOffsetFromCompositedAncestor(
       &owning_layer_, composited_ancestor,
-      local_raw_compositing_bounds.Location());
+      local_representative_point_for_fragmentation);
   snapped_offset_from_composited_ancestor =
       IntPoint(offset_from_composited_ancestor.X().Round(),
                offset_from_composited_ancestor.Y().Round());
@@ -904,6 +912,7 @@ void CompositedLayerMapping::ComputeBoundsOfOwningLayer(
 
   // Move the bounds by the subpixel accumulation so that it pixel-snaps
   // relative to absolute pixels instead of local coordinates.
+  LayoutRect local_raw_compositing_bounds = CompositedBounds();
   local_raw_compositing_bounds.Move(subpixel_accumulation);
   local_bounds = PixelSnappedIntRect(local_raw_compositing_bounds);