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

chrome/browser/sync/test/integration/two_client_wifi_credentials_sync_test.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/command_line.h"
 #include "base/macros.h"
 #include "chrome/browser/sync/test/integration/sync_test.h"
 #include "chrome/browser/sync/test/integration/wifi_credentials_helper.h"
 #include "chrome/common/chrome_switches.h"
 
 class TwoClientWifiCredentialsSyncTest : public SyncTest {
  public:
   TwoClientWifiCredentialsSyncTest() : SyncTest(TWO_CLIENT) {}
   ~TwoClientWifiCredentialsSyncTest() override {}
 
-  void SetUpCommandLine(CommandLine* command_line) override {
+  void SetUpCommandLine(base::CommandLine* command_line) override {
     SyncTest::SetUpCommandLine(command_line);
     command_line->AppendSwitch(switches::kEnableWifiCredentialSync);
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(TwoClientWifiCredentialsSyncTest);
 };
 
 IN_PROC_BROWSER_TEST_F(TwoClientWifiCredentialsSyncTest, NoCredentials) {
   ASSERT_TRUE(SetupSync()) << "SetupSync() failed.";
   ASSERT_TRUE(wifi_credentials_helper::VerifierIsEmpty());
   ASSERT_TRUE(wifi_credentials_helper::AllProfilesMatch());
 }