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

tools/gn/command_refs.cc

Index: tools/gn/command_refs.cc
diff --git a/tools/gn/command_refs.cc b/tools/gn/command_refs.cc
index 5c15a3432abb096e7ed1c9f6c0ee7105a3cdfd4d..01e2d61135c04ac17d442a6b5723644fa2d4e258 100644
--- a/tools/gn/command_refs.cc
+++ b/tools/gn/command_refs.cc
@@ -287,7 +287,7 @@ int RunRefs(const std::vector<std::string>& args) {
     return 1;
   }
 
-  const CommandLine* cmdline = CommandLine::ForCurrentProcess();
+  const base::CommandLine* cmdline = base::CommandLine::ForCurrentProcess();
   bool tree = cmdline->HasSwitch("tree");
   bool all = cmdline->HasSwitch("all");
   bool all_toolchains = cmdline->HasSwitch("all-toolchains");