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

chrome/browser/dom_distiller/tab_utils_browsertest.cc

Index: chrome/browser/dom_distiller/tab_utils_browsertest.cc
diff --git a/chrome/browser/dom_distiller/tab_utils_browsertest.cc b/chrome/browser/dom_distiller/tab_utils_browsertest.cc
index 6620b6dbe27a2de74a4bcd512baf554fb299caa1..d8a5d1347160cbb083dd78e7c1bd7985e8bdd587 100644
--- a/chrome/browser/dom_distiller/tab_utils_browsertest.cc
+++ b/chrome/browser/dom_distiller/tab_utils_browsertest.cc
@@ -32,7 +32,7 @@ const char* kSimpleArticlePath = "/dom_distiller/simple_article.html";
 
 class DomDistillerTabUtilsBrowserTest : public InProcessBrowserTest {
  public:
-  void SetUpCommandLine(CommandLine* command_line) override {
+  void SetUpCommandLine(base::CommandLine* command_line) override {
     command_line->AppendSwitch(switches::kEnableDomDistiller);
   }
 };