Do not show 'Print Preview' flag in about::flags of CrOS.

chrome/browser/about_flags.cc

 // Copyright (c) 2011 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 "chrome/browser/about_flags.h"
 
 #include <algorithm>
 #include <iterator>
 #include <map>
 #include <set>
@@ skipping 176 matching lines @@
   //   "webgl",
   //   IDS_FLAGS_WEBGL_NAME,
   //   IDS_FLAGS_WEBGL_DESCRIPTION,
   //   kOsAll,
   //   SINGLE_VALUE_TYPE(switches::kDisableExperimentalWebGL)
   // }
   {
     "print-preview",  // FLAGS:RECORD_UMA
     IDS_FLAGS_PRINT_PREVIEW_NAME,
     IDS_FLAGS_PRINT_PREVIEW_DESCRIPTION,
-    kOsAll,
+    kOsMac | kOsWin | kOsLinux, // This switch is not available in CrOS.
     SINGLE_VALUE_TYPE(switches::kEnablePrintPreview)
   },
   {
     "enable-nacl",  // FLAGS:RECORD_UMA
     IDS_FLAGS_ENABLE_NACL_NAME,
     IDS_FLAGS_ENABLE_NACL_DESCRIPTION,
     kOsAll,
     SINGLE_VALUE_TYPE(switches::kEnableNaCl)
   },
   {
@@ skipping 518 matching lines @@
 }
 
 const Experiment* GetExperiments(size_t* count) {
   *count = num_experiments;
   return experiments;
 }
 
 }  // namespace testing
 
 }  // namespace about_flags