Use effective columns when cells with colspan are present.

LayoutTests/accessibility/table-cells-with-colspan-expected.txt

Index: LayoutTests/accessibility/table-cells-with-colspan-expected.txt
diff --git a/LayoutTests/accessibility/table-cells-with-colspan-expected.txt b/LayoutTests/accessibility/table-cells-with-colspan-expected.txt
new file mode 100644
index 0000000000000000000000000000000000000000..ff9f7f38823cdfe0cc9f99542a2074d7b57bca6d
--- /dev/null
+++ b/LayoutTests/accessibility/table-cells-with-colspan-expected.txt
@@ -0,0 +1,27 @@
+data	col heada	data
+data	col head
+col head	col head
+Check whether cells with colspan are reported properly
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+PASS table1.columnCount is 3
+PASS cell_0_0.role is 'AXRole: AXCell'
+PASS cell_0_0.columnIndexRange() is '{0, 1}'
+PASS cell_0_1.role is 'AXRole: AXColumnHeader'
+PASS cell_0_1.columnIndexRange() is '{1, 1}'
+PASS cell_0_2.role is 'AXRole: AXCell'
+PASS cell_0_2.columnIndexRange() is '{2, 1}'
+PASS table2.columnCount is 3
+PASS table2.columnHeadersCount is 3
+PASS cell_0_1.columnIndexRange() is '{1, 2}'
+PASS cell_0_2.columnIndexRange() is '{1, 2}'
+PASS table2.columnHeaderAtIndex(0).isEqual(cell_0_1) is true
+PASS table2.columnHeaderAtIndex(0).isEqual(cell_0_2) is true
+PASS table2.columnHeaderAtIndex(1).isEqual(table2.cellForColumnAndRow(1, 1)) is true
+PASS table2.columnHeaderAtIndex(2).isEqual(table2.cellForColumnAndRow(2, 1)) is true
+PASS successfullyParsed is true
+
+TEST COMPLETE
+