Make callers of CommandLine use it via the base:: namespace.

tools/gn/scheduler.cc

Index: tools/gn/scheduler.cc
diff --git a/tools/gn/scheduler.cc b/tools/gn/scheduler.cc
index 0f6965420e8416c02336e43c8ac760297c9ef643..b453c9c95f1fd847ca975d7b8370065f28f7feb9 100644
--- a/tools/gn/scheduler.cc
+++ b/tools/gn/scheduler.cc
@@ -16,7 +16,8 @@ namespace {
 
 int GetThreadCount() {
   std::string thread_count =
-      CommandLine::ForCurrentProcess()->GetSwitchValueASCII(switches::kThreads);
+      base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
+          switches::kThreads);
 
   int result;
   if (thread_count.empty() || !base::StringToInt(thread_count, &result))