patch from petermayo to fix GN dependency regeneration

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 591947d38cae9ca29918c11fc7697625fd56a229..500f05575bae02e57ec87ca369fc3836ad625073 100644
--- a/tools/gn/ninja_build_writer.cc
+++ b/tools/gn/ninja_build_writer.cc
@@ -77,6 +77,15 @@ std::string GetSelfInvocationCommand(const BuildSettings* build_settings) {
 #endif
 }
 
+void WriteAnotherFile(std::ostream& out, const base::FilePath& name,
+                      EscapingMode mode) {
+  EscapeOptions path_escaping;
+  path_escaping.mode = mode;
+
+  out << " ";
+  EscapeStringToStream(out, FilePathToUTF8(name), path_escaping);
+}
+
 }  // namespace
 
 NinjaBuildWriter::NinjaBuildWriter(
@@ -143,10 +152,20 @@ bool NinjaBuildWriter::RunAndWriteFile(
 void NinjaBuildWriter::WriteNinjaRules() {
   out_ << "rule gn\n";
   out_ << "  command = " << GetSelfInvocationCommand(build_settings_) << "\n";
-  out_ << "  description = Regenerating ninja files\n\n";
+  out_ << "  description = Regenerating ninja files\n";
+  out_ << "  restat = 1\n\n";
+
+  // This rule will regenerate the ninja files when any input file has changed,
+  // or is missing.
+  out_ << "build build.ninja";
+
+  // Other files read by the build.
+  std::vector<SourceFile> written_files = g_scheduler->GetWrittenFiles();
+  for (const auto& written_file : written_files)
+    WriteAnotherFile(out_, build_settings_->GetFullPath(written_file),
+                     ESCAPE_NINJA_COMMAND);
 
-  // This rule will regenerate the ninja files when any input file has changed.
-  out_ << "build build.ninja: gn\n"
+  out_ << ": gn\n"
        << "  generator = 1\n"
        << "  depfile = build.ninja.d\n";
 
@@ -158,12 +177,12 @@ void NinjaBuildWriter::WriteNinjaRules() {
   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);
+    WriteAnotherFile(dep_out_, input_file, ESCAPE_NONE);
 
   // 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);
+    WriteAnotherFile(dep_out_, other_file, ESCAPE_NONE);
 
   out_ << std::endl;
 }