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

content/browser/cross_site_transfer_browsertest.cc

Index: content/browser/cross_site_transfer_browsertest.cc
diff --git a/content/browser/cross_site_transfer_browsertest.cc b/content/browser/cross_site_transfer_browsertest.cc
index f611030bf9a93355ca01e164068d5922ff51681d..67793e3f74737f0992cd055e26452dcb9308f0fa 100644
--- a/content/browser/cross_site_transfer_browsertest.cc
+++ b/content/browser/cross_site_transfer_browsertest.cc
@@ -204,7 +204,7 @@ class CrossSiteTransferTest : public ContentBrowserTest {
       load_observer.Wait();
   }
 
-  void SetUpCommandLine(CommandLine* command_line) override {
+  void SetUpCommandLine(base::CommandLine* command_line) override {
     // Use --site-per-process to force process swaps for cross-site transfers.
     command_line->AppendSwitch(switches::kSitePerProcess);
   }