GN: Makes GN output deterministic

tools/gn/ninja_build_writer.cc

Index: tools/gn/ninja_build_writer.cc
diff --git a/tools/gn/ninja_build_writer.cc b/tools/gn/ninja_build_writer.cc
index 50638fbb7876819438dea2b6dbe659779da72731..39a27d3a997a65aa7153892e35df0496a6678a6b 100644
--- a/tools/gn/ninja_build_writer.cc
+++ b/tools/gn/ninja_build_writer.cc
@@ -194,13 +194,17 @@ void NinjaBuildWriter::WriteNinjaRules() {
   dep_out_ << "build.ninja:";
   std::vector<base::FilePath> input_files;
   g_scheduler->input_file_manager()->GetAllPhysicalInputFileNames(&input_files);
-  for (const auto& input_file : input_files)
-    dep_out_ << " " << FilePathToUTF8(input_file);
+
+  // Keep the files sorted to ensure output is deterministic.

[mithro-old, 2015/12/03 05:20:31]

If you are assuming the input is sorted here, it probably makes sense to DCHECK
it here?

[Zachary Forman, 2015/12/03 07:27:02]

Poorly phrased - we place the filepaths into a set to ensure that they're
sorted.

I've updated the comment.

+  std::set<base::FilePath> file_set(input_files.begin(), input_files.end());
 
   // Other files read by the build.
-  std::vector<base::FilePath> other_files = g_scheduler->GetGenDependencies();
-  for (const auto& other_file : other_files)
-    dep_out_ << " " << FilePathToUTF8(other_file);
+  input_files = g_scheduler->GetGenDependencies();
+
+  file_set.insert(input_files.begin(), input_files.end());
+
+  for (const auto& input_file : file_set)
+    dep_out_ << " " << FilePathToUTF8(input_file);
 
   out_ << std::endl;
 }