GN: Use all targets to determine whether a file is generated (for `check`).

tools/gn/header_checker.cc

Index: tools/gn/header_checker.cc
diff --git a/tools/gn/header_checker.cc b/tools/gn/header_checker.cc
index b15b4fa16b2b88aaf91d57426adf8a225c6f9a0d..72cc6e2426f45d6b97bfb1aa99e79261bab470bc 100644
--- a/tools/gn/header_checker.cc
+++ b/tools/gn/header_checker.cc
@@ -163,9 +163,10 @@ void HeaderChecker::RunCheckOverFiles(const FileMap& files, bool force_check) {
         type != SOURCE_M && type != SOURCE_MM && type != SOURCE_RC)
       continue;
 
-    // If any target marks it as generated, don't check it.
+    // If any target marks it as generated, don't check it. We have to check
+    // the file map which includes all targets, not just those being checked.

[brettw, 2015/11/28 17:51:33]

CAn you be explicit in the comment here that 'files' contains the files being
checked, while file_map_ contains all known files?

[jbroman, 2015/11/30 15:25:05]

Done.

     bool is_generated = false;
-    for (const auto& vect_i : file.second)
+    for (const auto& vect_i : file_map_[file.first])
       is_generated |= vect_i.is_generated;
     if (is_generated)
       continue;