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

tools/gn/trace.cc

Index: tools/gn/trace.cc
diff --git a/tools/gn/trace.cc b/tools/gn/trace.cc
index 530915137b3e6a822a17844f480da748fff3631e..283c2fa892711dc7c256d41bba795cc5ca8735ea 100644
--- a/tools/gn/trace.cc
+++ b/tools/gn/trace.cc
@@ -147,7 +147,7 @@ void ScopedTrace::SetToolchain(const Label& label) {
     item_->set_toolchain(label.GetUserVisibleName(false));
 }
 
-void ScopedTrace::SetCommandLine(const CommandLine& cmdline) {
+void ScopedTrace::SetCommandLine(const base::CommandLine& cmdline) {
   if (item_)
     item_->set_cmdline(FilePathToUTF8(cmdline.GetArgumentsString()));
 }