Acquire lock in Args::SetSystemVars()

tools/gn/args.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "tools/gn/args.h"
 
 #include "build/build_config.h"
 #include "tools/gn/variables.h"
 
 #if defined(OS_WIN)
@@ skipping 145 matching lines @@
           "The variable \"" + i->first.as_string() + "\" was set as a build "
           "argument\nbut never appeared in a declare_args() block in any "
           "buildfile.");
       return false;
     }
   }
   return true;
 }
 
 void Args::SetSystemVars(Scope* dest) const {
+  base::AutoLock lock(lock_);
+
   // Host OS.
   const char* os = NULL;
 #if defined(OS_WIN)
   os = "win";
 #elif defined(OS_MACOSX)
   os = "mac";
 #elif defined(OS_LINUX)
   os = "linux";
 #else
   #error Unknown OS type.
@@ skipping 64 matching lines @@
        i != values.end(); ++i)
     scope->SetValue(i->first, i->second, i->second.origin());
 }
 
 void Args::SaveOverrideRecord(const Scope::KeyValueMap& values) const {
   base::AutoLock lock(lock_);
   for (Scope::KeyValueMap::const_iterator i = values.begin();
        i != values.end(); ++i)
     all_overrides_[i->first] = i->second;
 }