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

tools/gn/gn_main.cc

Index: tools/gn/gn_main.cc
diff --git a/tools/gn/gn_main.cc b/tools/gn/gn_main.cc
index 6a409f9d509f0051a3110f9453b5044a818869c7..50d55e72a7239542a924eaf8c878d0b9f211f2e8 100644
--- a/tools/gn/gn_main.cc
+++ b/tools/gn/gn_main.cc
@@ -21,8 +21,8 @@
 
 namespace {
 
-std::vector<std::string> GetArgs(const CommandLine& cmdline) {
-  CommandLine::StringVector in_args = cmdline.GetArgs();
+std::vector<std::string> GetArgs(const base::CommandLine& cmdline) {
+  base::CommandLine::StringVector in_args = cmdline.GetArgs();
 #if defined(OS_WIN)
   std::vector<std::string> out_args;
   for (const auto& arg : in_args)
@@ -38,11 +38,11 @@ std::vector<std::string> GetArgs(const CommandLine& cmdline) {
 int main(int argc, char** argv) {
   base::AtExitManager at_exit;
 #if defined(OS_WIN)
-  CommandLine::set_slash_is_not_a_switch();
+  base::CommandLine::set_slash_is_not_a_switch();
 #endif
-  CommandLine::Init(argc, argv);
+  base::CommandLine::Init(argc, argv);
 
-  const CommandLine& cmdline = *CommandLine::ForCurrentProcess();
+  const base::CommandLine& cmdline = *base::CommandLine::ForCurrentProcess();
   std::vector<std::string> args = GetArgs(cmdline);
 
   std::string command;