Remove the enable_task_manager build flag and define.

chrome/browser/prefs/browser_prefs.cc

 // Copyright 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/prefs/browser_prefs.h"
 
 #include <string>
 
 #include "base/files/file_util.h"
 #include "base/metrics/histogram_macros.h"
@@ skipping 368 matching lines @@
 #endif
 
 #if BUILDFLAG(ENABLE_PLUGINS)
   PluginFinder::RegisterPrefs(registry);
 #endif
 
 #if BUILDFLAG(ENABLE_PLUGIN_INSTALLATION)
   PluginsResourceService::RegisterPrefs(registry);
 #endif
 
-#if defined(ENABLE_TASK_MANAGER)
+#if !defined(OS_ANDROID)
   task_manager::TaskManagerInterface::RegisterPrefs(registry);
-#endif  // defined(ENABLE_TASK_MANAGER)
+#endif  // !defined(OS_ANDROID)
 
 #if BUILDFLAG(ENABLE_BACKGROUND)
   BackgroundModeManager::RegisterPrefs(registry);
 #endif
 
 #if !defined(OS_ANDROID)
   RegisterBrowserPrefs(registry);
   StartupBrowserCreator::RegisterLocalStatePrefs(registry);
   // The native GCM is used on Android instead.
   gcm::GCMChannelStatusSyncer::RegisterPrefs(registry);
@@ skipping 378 matching lines @@
   // Added 8/2016.
   profile_prefs->ClearPref(kStaticEncodings);
   profile_prefs->ClearPref(kRecentlySelectedEncoding);
 
   // Added 9/2016.
   profile_prefs->ClearPref(kWebKitUsesUniversalDetector);
   profile_prefs->ClearPref(kWebKitAllowDisplayingInsecureContent);
 }
 
 }  // namespace chrome