Correct conversion from flowthread to visual coordinate space when there's border/padding.

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

Index: third_party/WebKit/Source/core/layout/MultiColumnFragmentainerGroup.cpp
diff --git a/third_party/WebKit/Source/core/layout/MultiColumnFragmentainerGroup.cpp b/third_party/WebKit/Source/core/layout/MultiColumnFragmentainerGroup.cpp
index 0f58fcefb2f47427dee04a82f6e45825e6635c00..67822a18db4472af67da201c0e3cd459824763c1 100644
--- a/third_party/WebKit/Source/core/layout/MultiColumnFragmentainerGroup.cpp
+++ b/third_party/WebKit/Source/core/layout/MultiColumnFragmentainerGroup.cpp
@@ -110,10 +110,11 @@ LayoutSize MultiColumnFragmentainerGroup::flowThreadTranslationAtOffset(LayoutUn
 
     LayoutSize enclosingTranslation;
     if (LayoutMultiColumnFlowThread* enclosingFlowThread = flowThread->enclosingFlowThread()) {
+        const MultiColumnFragmentainerGroup& firstRow = flowThread->firstMultiColumnSet()->firstFragmentainerGroup();
         // Translation that would map points in the coordinate space of the outermost flow thread to
         // visual points in the first column in the first fragmentainer group (row) in our multicol
         // container.
-        LayoutSize enclosingTranslationOrigin = enclosingFlowThread->flowThreadTranslationAtOffset(flowThread->blockOffsetInEnclosingFragmentationContext());
+        LayoutSize enclosingTranslationOrigin = enclosingFlowThread->flowThreadTranslationAtOffset(firstRow.blockOffsetInEnclosingFragmentationContext());
 
         // Translation that would map points in the coordinate space of the outermost flow thread to
         // visual points in the first column in this fragmentainer group.