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..f33fec065c8bd83c2b318d57d362d3e54d63f5d8 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 +62,11 @@ bool NinjaToolchainWriter::RunAndWriteFile(
   if (file.fail())
     return false;
 
+  // Sort targets so that they are in a deterministic order.

[M-A Ruel, 2015/12/07 15:09:50]

I'd still prefer:
DCHECK(
    std::is_sorted(targets.begin(), targets.end(),
    [](const Target* a, const Target* b) { return a->label() < b->label(); }));

remove the const and enforce caller to fix their code.

But in fact you really don't need to change this file at all, see the other
comment.

[Zachary Forman, 2015/12/08 09:40:42]

I've followed your advice here and effectively removed all changes to this file.

+  std::sort(
+      targets.begin(), targets.end(),
+      [](const Target* a, const Target* b) { return a->label() < b->label(); });
+
   NinjaToolchainWriter gen(settings, toolchain, targets, file);
   gen.Run();
   return true;