tools/gn: rename char_offset to column_number

tools/gn/c_include_iterator_unittest.cc

Index: tools/gn/c_include_iterator_unittest.cc
diff --git a/tools/gn/c_include_iterator_unittest.cc b/tools/gn/c_include_iterator_unittest.cc
index 1add29b53aab8541408aa848968c51c3d973814f..98458b9e6c21c5dd3f91c15b0457dad57c9b129f 100644
--- a/tools/gn/c_include_iterator_unittest.cc
+++ b/tools/gn/c_include_iterator_unittest.cc
@@ -13,8 +13,8 @@ bool RangeIs(const LocationRange& range,
              int line, int begin_char, int end_char) {
   return range.begin().line_number() == line &&
          range.end().line_number() == line &&
-         range.begin().char_offset() == begin_char &&
-         range.end().char_offset() == end_char;
+         range.begin().column_number() == begin_char &&
+         range.end().column_number() == end_char;
 }
 
 }  // namespace