Add a policy to always show the Cast toolbar icon

chrome/browser/policy/configuration_policy_handler_list_factory.cc

 // Copyright 2013 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/policy/configuration_policy_handler_list_factory.h"
 
 #include <limits.h>
 #include <stddef.h>
 
 #include <utility>
@@ skipping 393 matching lines @@
   { key::kSSLVersionMax,
     ssl_config::prefs::kSSLVersionMax,
     base::Value::Type::STRING },
   { key::kNTPContentSuggestionsEnabled,
     ntp_snippets::prefs::kEnableSnippets,
     base::Value::Type::BOOLEAN },
 #if defined(ENABLE_MEDIA_ROUTER)
   { key::kEnableMediaRouter,
     prefs::kEnableMediaRouter,
     base::Value::Type::BOOLEAN },
+#if !defined(OS_ANDROID)
+  { key::kShowCastIconInToolbar,
+    prefs::kShowCastIconInToolbar,
+    base::Value::Type::BOOLEAN },
+#endif  // !defined(OS_ANDROID)
 #endif  // defined(ENABLE_MEDIA_ROUTER)
 #if BUILDFLAG(ENABLE_WEBRTC)
   { key::kWebRtcUdpPortRange,
     prefs::kWebRTCUDPPortRange,
     base::Value::Type::STRING },
 #endif  // BUILDFLAG(ENABLE_WEBRTC)
 #if !defined(OS_MACOSX)
   { key::kFullscreenAllowed,
     prefs::kFullscreenAllowed,
     base::Value::Type::BOOLEAN },
@@ skipping 577 matching lines @@
 #endif  // defined(OS_CHROMEOS)
 
 #if BUILDFLAG(ENABLE_PLUGINS)
   handlers->AddHandler(base::MakeUnique<PluginPolicyHandler>());
 #endif  // BUILDFLAG(ENABLE_PLUGINS)
 
   return handlers;
 }
 
 }  // namespace policy