tools/gn: rename char_offset to column_number

tools/gn/string_utils.cc

Index: tools/gn/string_utils.cc
diff --git a/tools/gn/string_utils.cc b/tools/gn/string_utils.cc
index 496970bcc00819c9c4da77f381d28259d967107c..9b0eb264f15eaef15aa053eeb4ed9a709bab98b5 100644
--- a/tools/gn/string_utils.cc
+++ b/tools/gn/string_utils.cc
@@ -23,12 +23,13 @@ Err ErrInsideStringToken(const Token& token, size_t offset, size_t size,
   int int_offset = static_cast<int>(offset);
   Location begin_loc(token.location().file(),
                      token.location().line_number(),
-                     token.location().char_offset() + int_offset + 1,
+                     token.location().column_number() + int_offset + 1,
                      token.location().byte() + int_offset + 1);
   Location end_loc(
       token.location().file(),
       token.location().line_number(),
-      token.location().char_offset() + int_offset + 1 + static_cast<int>(size),
+      token.location().column_number() + int_offset + 1 +
+          static_cast<int>(size),
       token.location().byte() + int_offset + 1 + static_cast<int>(size));
   return Err(LocationRange(begin_loc, end_loc), msg, help);
 }