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

chrome/browser/dom_distiller/dom_distiller_viewer_source_browsertest.cc

Index: chrome/browser/dom_distiller/dom_distiller_viewer_source_browsertest.cc
diff --git a/chrome/browser/dom_distiller/dom_distiller_viewer_source_browsertest.cc b/chrome/browser/dom_distiller/dom_distiller_viewer_source_browsertest.cc
index 6729ed22e0e871973a224b7f2430a861ea465285..4ad5f69ee8bd2824bbb11d24508dacbfcef783d1 100644
--- a/chrome/browser/dom_distiller/dom_distiller_viewer_source_browsertest.cc
+++ b/chrome/browser/dom_distiller/dom_distiller_viewer_source_browsertest.cc
@@ -87,7 +87,7 @@ class DomDistillerViewerSourceBrowserTest : public InProcessBrowserTest {
 
   void TearDownOnMainThread() override { delete database_model_; }
 
-  void SetUpCommandLine(CommandLine* command_line) override {
+  void SetUpCommandLine(base::CommandLine* command_line) override {
     command_line->AppendSwitch(switches::kEnableDomDistiller);
   }