gn: attach comments to parse tree

tools/gn/location.cc

Index: tools/gn/location.cc
diff --git a/tools/gn/location.cc b/tools/gn/location.cc
index 61f22b5e079d2c273b189192f09eb361e6acf7ea..e4dbc10c59ba1bff3624124a2e376f6e14d3203d 100644
--- a/tools/gn/location.cc
+++ b/tools/gn/location.cc
@@ -14,10 +14,14 @@ Location::Location()
       char_offset_(-1) {
 }
 
-Location::Location(const InputFile* file, int line_number, int char_offset)
+Location::Location(const InputFile* file,
+                   int line_number,
+                   int char_offset,
+                   int byte)
     : file_(file),
       line_number_(line_number),
-      char_offset_(char_offset) {
+      char_offset_(char_offset),
+      byte_(byte) {
 }
 
 bool Location::operator==(const Location& other) const {