Hardcode extensions::util::IsNewBookmarkAppsEnabled() to true, except on Mac.

chrome/browser/chrome_content_browser_client.cc

 // Copyright (c) 2012 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/chrome_content_browser_client.h"
 
 #include <map>
 #include <set>
 #include <utility>
 #include <vector>
@@ skipping 1844 matching lines @@
       extensions::switches::kNativeCrxBindings,
       extensions::switches::kWhitelistedExtensionID,
 #endif
       switches::kAllowInsecureLocalhost,
       switches::kAppsGalleryURL,
       switches::kCloudPrintURL,
       switches::kCloudPrintXmppEndpoint,
       switches::kDisableBundledPpapiFlash,
       switches::kDisableCastStreamingHWEncoding,
       switches::kDisableJavaScriptHarmonyShipping,
-      switches::kDisableNewBookmarkApps,

[tapted, 2017/03/22 02:34:02]

Using base::Feature allows this stuff to happen automatically when
RenderProcessHostImpl::PropagateBrowserCommandLineToRenderer(..) does
BrowserChildProcessHostImpl::CopyFeatureAndFieldTrialFlags(..)

       switches::kEnableBenchmarking,
       switches::kEnableDistillabilityService,
       switches::kEnableNaCl,
 #if !defined(DISABLE_NACL)
       switches::kEnableNaClDebug,
       switches::kEnableNaClNonSfiMode,
 #endif
       switches::kEnableNetBenchmarking,
-      switches::kEnableNewBookmarkApps,
 #if !defined(DISABLE_NACL)
       switches::kForcePNaClSubzero,
 #endif
       switches::kJavaScriptHarmony,
       switches::kOriginTrialDisabledFeatures,
       switches::kOriginTrialPublicKey,
       switches::kPpapiFlashArgs,
       switches::kPpapiFlashPath,
       switches::kPpapiFlashVersion,
       switches::kProfilingAtStart,
@@ skipping 1668 matching lines @@
     RedirectNonUINonIOBrowserThreadsToTaskScheduler() {
   return variations::GetVariationParamValue(
              "BrowserScheduler", "RedirectNonUINonIOBrowserThreads") == "true";
 }
 
 // static
 void ChromeContentBrowserClient::SetDefaultQuotaSettingsForTesting(
     const storage::QuotaSettings* settings) {
   g_default_quota_settings = settings;
 }