CommandLine: add a CopySwitchesFrom() for copying from another CommandLine

chrome/browser/printing/printing_layout_uitest.cc

 // Copyright (c) 2006-2009 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/file_util.h"
 #include "base/simple_thread.h"
 #include "base/test/test_file_util.h"
 #include "base/win_util.h"
 #include "chrome/common/chrome_paths.h"
@@ skipping 10 matching lines @@
 namespace {
 
 using printing::Image;
 
 const char kGenerateSwitch[] = "print-layout-generate";
 const wchar_t kDocRoot[] = L"chrome/test/data";
 
 class PrintingLayoutTest : public PrintingTest<UITest> {
  public:
   PrintingLayoutTest() {
-    emf_path_ = browser_directory_;
-    emf_path_ = emf_path_.AppendASCII("metafile_dumps");
-    launch_arguments_.AppendSwitchWithValue("debug-print",
-                                            L'"' + emf_path_.value() + L'"');
+    emf_path_ = browser_directory_.AppendASCII("metafile_dumps");
+    launch_arguments_.AppendSwitchPath("debug-print", emf_path_);
     show_window_ = true;
   }
 
   virtual void SetUp() {
     // Make sure there is no left overs.
     CleanupDumpDirectory();
     UITest::SetUp();
   }
 
   virtual void TearDown() {
@@ skipping 380 matching lines @@
 
     // Force a navigation elsewhere to verify that it's fine with it.
     url = server->TestServerPage("files/printing/test1.html");
     EXPECT_EQ(AUTOMATION_MSG_NAVIGATION_SUCCESS,
               tab_proxy->NavigateToURL(url));
   }
   CloseBrowserAndServer();
 
   EXPECT_EQ(0., CompareWithResult(L"iframe")) << L"iframe";
 }