Make extensions developer mode adhere to policy

chrome/browser/extensions/api/developer_private/developer_private_api.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/extensions/api/developer_private/developer_private_api.h"
 
 #include <stddef.h>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 146 matching lines @@
   UMA_HISTOGRAM_BOOLEAN("ExtensionSettings.ShouldDoVerificationCheck",
                         should_do_verification_check);
   if (should_do_verification_check)
     InstallVerifier::Get(context)->VerifyAllExtensions();
 }
 
 std::unique_ptr<developer::ProfileInfo> CreateProfileInfo(Profile* profile) {
   std::unique_ptr<developer::ProfileInfo> info(new developer::ProfileInfo());
   info->is_supervised = profile->IsSupervised();
   PrefService* prefs = profile->GetPrefs();
+  const PrefService::Preference* pref =
+      prefs->FindPreference(prefs::kExtensionsUIDeveloperMode);
   info->is_incognito_available =
       IncognitoModePrefs::GetAvailability(prefs) !=
           IncognitoModePrefs::DISABLED;
+  info->is_developer_mode_disabled_by_policy = pref && pref->IsManaged();

[Bernhard Bauer, 2016/11/28 17:11:03]

When would the preference not be found? Usually we treat the set of registered
preferences as fixed at compile time, so a missing preference shouldn't (need
to) be handled. If there is a test that crashes here, you might have to register
preferences on the profile first?

[pmarko, 2016/11/29 12:40:21]

Good point, tests were working fine, this was just me being overly cautious
because I'm new :)
Done.

   info->in_developer_mode =
       !info->is_supervised &&
       prefs->GetBoolean(prefs::kExtensionsUIDeveloperMode);
   info->app_info_dialog_enabled = CanShowAppInfoDialog();
   info->can_load_unpacked =
       !ExtensionManagementFactory::GetForBrowserContext(profile)
           ->BlacklistedByDefault();
   return info;
 }
 
@@ skipping 411 matching lines @@
 
 ExtensionFunction::ResponseAction
 DeveloperPrivateUpdateProfileConfigurationFunction::Run() {
   std::unique_ptr<developer::UpdateProfileConfiguration::Params> params(
       developer::UpdateProfileConfiguration::Params::Create(*args_));
   EXTENSION_FUNCTION_VALIDATE(params);
 
   const developer::ProfileConfigurationUpdate& update = params->update;
   PrefService* prefs = GetProfile()->GetPrefs();
   if (update.in_developer_mode) {
     if (GetProfile()->IsSupervised())

[Devlin, 2016/11/28 17:34:01]

We should add a check here.  Otherwise, the only guards we have against this are
in JS, and that's very weak if anyone opens the developer console (e.g. the user
could just type
chrome.developerPrivate.updateProfileConfiguration({in_developer_mode: true})
and never have to hit the checkbox).

I realize that, right now, these prefs are actually piggy backing, so
theoretically the user might not be able to open the console, but that's a
pretty weak guarantee, and very subject to change.  Enforcing this at the C++
level is much less likely to be circumvented. :)

[pmarko, 2016/11/29 12:40:21]

I'm not sure it's necessary -- I had a check here back in patchset 3 when the
plan was to set the pref to false explicitly.

Now that it is set through ConfigurationPolicyPrefStore (see
configuration_policy_handler_list_factory.cc), the policy-controlled pref value
overrides any value set here, so I removed the check.
If the user passes that JS, he will only affect the value the pref has after the
policy will be removed. 
So I think it should not be possible to trigger it that way when the policy is
in place. Or am I missing something?

[Devlin, 2016/11/30 19:19:50]

I'll trust you and bauerb - my pref knowledge is limited. :)  In either case,
seems like a developerPrivate unittest would still be useful?  Making sure we
behave as expected when passed unexpected values?

[pmarko, 2016/12/02 00:20:07]

Sorry, I almost forgot -- added.

       return RespondNow(Error(kCannotUpdateSupervisedProfileSettingsError));
     prefs->SetBoolean(prefs::kExtensionsUIDeveloperMode,
                       *update.in_developer_mode);
   }
 
   return RespondNow(NoArguments());
 }
 
 DeveloperPrivateUpdateExtensionConfigurationFunction::
 ~DeveloperPrivateUpdateExtensionConfigurationFunction() {}
@@ skipping 841 matching lines @@
         update.extension_id, update.command_name, *update.keybinding);
   }
 
   return RespondNow(NoArguments());
 }
 
 
 }  // namespace api
 
 }  // namespace extensions