GN: Makes GN output deterministic

tools/gn/ninja_toolchain_writer.cc

Index: tools/gn/ninja_toolchain_writer.cc
diff --git a/tools/gn/ninja_toolchain_writer.cc b/tools/gn/ninja_toolchain_writer.cc
index e7459ebb3cfa2ede1e0d5303aedfdf0b36e134b2..d3b65dbbcb90bcf3b36b194fdc6bc33d1315aa56 100644
--- a/tools/gn/ninja_toolchain_writer.cc
+++ b/tools/gn/ninja_toolchain_writer.cc
@@ -49,7 +49,7 @@ void NinjaToolchainWriter::Run() {
 bool NinjaToolchainWriter::RunAndWriteFile(
     const Settings* settings,
     const Toolchain* toolchain,
-    const std::vector<const Target*>& targets) {
+    std::vector<const Target*>& targets) {
   base::FilePath ninja_file(settings->build_settings()->GetFullPath(
       GetNinjaFileForToolchain(settings)));
   ScopedTrace trace(TraceItem::TRACE_FILE_WRITE, FilePathToUTF8(ninja_file));
@@ -62,6 +62,9 @@ bool NinjaToolchainWriter::RunAndWriteFile(
   if (file.fail())
     return false;
 
+  // Sort here to ensure the files are deterministically ordered.

[M-A Ruel, 2015/12/07 00:20:16]

You could DCHECK instead that the list is sorted. I'd prefer that to mutating
the inputs.

[Zachary Forman, 2015/12/07 03:18:17]

This is poor phrasing on my part - they come in unsorted and leave sorted.
Making a copy is probably cheap enough, though.

+  std::sort(targets.begin(), targets.end(), DereferenceComparator<Target>());
+
   NinjaToolchainWriter gen(settings, toolchain, targets, file);
   gen.Run();
   return true;