Fix table cell background painting

third_party/WebKit/Source/core/layout/LayoutTableCol.h

Index: third_party/WebKit/Source/core/layout/LayoutTableCol.h
diff --git a/third_party/WebKit/Source/core/layout/LayoutTableCol.h b/third_party/WebKit/Source/core/layout/LayoutTableCol.h
index a028b3b73ac374db8fd72ff02c5fd5b908f956bd..306ff030e64521d9ea1f69973a06205b5737a2fe 100644
--- a/third_party/WebKit/Source/core/layout/LayoutTableCol.h
+++ b/third_party/WebKit/Source/core/layout/LayoutTableCol.h
@@ -76,11 +76,12 @@ public:
     // For CSS table columns or colgroups, this is always 1.
     unsigned span() const { return m_span; }
 
-    bool isTableColumnGroupWithColumnChildren() { return firstChild(); }
+    bool isTableColumnGroupWithColumnChildren() const { return firstChild(); }
     bool isTableColumn() const { return style()->display() == TABLE_COLUMN; }
     bool isTableColumnGroup() const { return style()->display() == TABLE_COLUMN_GROUP; }
 
     LayoutTableCol* enclosingColumnGroup() const;
+    LayoutTableCol* lastColumnInGroup() const;
 
     // Returns the next column or column-group.
     LayoutTableCol* nextColumn() const;
@@ -92,6 +93,20 @@ public:
 
     const char* name() const override { return "LayoutTableCol"; }
 
+    // Returns col/colgroup table-relative position.
+    // <col> elements need to provide absoluteColumnIndex.

[Xianzhu, 2016/03/28 00:44:42]

Can you rephrase the above sentence?

[atotic1, 2016/03/29 17:05:16]

Done.

+    // This is because <col> element with span N is treated for display as
+    // N <col> elements with span 1. It does not make sense to talk
+    // about visual <col> position, only about <col> position at
+    // particular absolute column.

[Xianzhu, 2016/03/28 00:44:42]

I think you can omit the above comments.

[atotic1, 2016/03/29 17:05:16]

Moved it into .cpp. The comment describes a non-intuitive aspect of table spec.

+    LayoutRect positionByCellSpan(unsigned absoluteColumnIndex) const;
+
+    // Return indexes to all columns inside this element.
+    // Can return vector with size 0 if LayoutTableCol is out of range.
+    // <col> element can return size() > 1 if it spans multiple columns
+    // <colgroup> element can return any size.
+    Vector<unsigned> getEffectiveColumnIndexes() const;
+
 private:
     LayoutObjectChildList* virtualChildren() override { return children(); }
     const LayoutObjectChildList* virtualChildren() const override { return children(); }