Fix table cell background painting

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

Index: third_party/WebKit/Source/core/layout/LayoutTable.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutTable.cpp b/third_party/WebKit/Source/core/layout/LayoutTable.cpp
index bbcf8f535af38fc826047c784e00c1691ea15bf9..bd79793380f4e7d67571d1eb9aa278e18006cfe4 100644
--- a/third_party/WebKit/Source/core/layout/LayoutTable.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutTable.cpp
@@ -734,6 +734,14 @@ LayoutTableSection* LayoutTable::topNonEmptySection() const
     return section;
 }
 
+LayoutTableSection* LayoutTable::bottomNonEmptySection() const
+{
+    LayoutTableSection* section = bottomSection();
+    if (section && !section->numRows())
+        section = sectionAbove(section, SkipEmptySections);
+    return section;
+}
+
 void LayoutTable::splitEffectiveColumn(unsigned index, unsigned firstSpan)
 {
     // We split the column at |index|, taking |firstSpan| cells from the span.
@@ -844,6 +852,24 @@ LayoutTable::ColAndColGroup LayoutTable::slowColElementAtAbsoluteColumn(unsigned
     return ColAndColGroup();
 }
 
+// Maps LayoutTableCol => absoluteColumnIndex,
+// an inverse of slowColElementAtAbsoluteColumn.

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

Move the comment to header file.

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

Done.

+unsigned LayoutTable::colElementToAbsoluteColumn(const LayoutTableCol * colElement) const

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

Nit: remove the extra space before '*'.

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

Done.

+{
+    unsigned col = 0;
+
+    for (LayoutTableCol* columnLayoutObject = firstColumn(); columnLayoutObject; columnLayoutObject = columnLayoutObject->nextColumn()) {
+        if (columnLayoutObject == colElement)
+            break;

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

Change this to 'return col';

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

Done.

+        if (columnLayoutObject->isTableColumnGroupWithColumnChildren()) {
+            // Do nothing, span will increase with children

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

The comment is not clear to me. How about:
    // Count spans of leaf col elements only.
    if (!columnLayoutObject->isTableColumnGroupWithColumnChildren())
        col += columnLayoutObject->span();

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

Done.

+        } else {
+            col += columnLayoutObject->span();
+        }
+    }
+    return col;

[Xianzhu, 2016/03/28 00:44:41]

Change this to:
   ASSERT_NOT_REACHED();
   return 0;
to catch errors.

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

Done.

+}
+
 void LayoutTable::recalcSections() const
 {
     ASSERT(m_needsSectionRecalc);