Check that only a single delegate for the Android PolicyProvider exists.

components/policy/core/common/policy_provider_android.cc

 // Copyright 2014 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 "components/policy/core/common/policy_provider_android.h"
 #include "components/policy/core/common/policy_provider_android_delegate.h"
 
 namespace policy {
 
 namespace {
@@ skipping 14 matching lines @@
 }
 
 // static
 void PolicyProviderAndroid::SetShouldWaitForPolicy(
     bool should_wait_for_policy) {
   g_wait_for_policies = should_wait_for_policy;
 }
 
 void PolicyProviderAndroid::SetDelegate(
     PolicyProviderAndroidDelegate* delegate) {
+  DCHECK(!delegate || !delegate_);
   delegate_ = delegate;
 }
 
 void PolicyProviderAndroid::SetPolicies(scoped_ptr<PolicyBundle> policy) {
   initialized_ = true;
   UpdatePolicy(policy.Pass());
 }
 
 void PolicyProviderAndroid::Shutdown() {
   if (delegate_)
@@ skipping 12 matching lines @@
     delegate_->RefreshPolicies();
   } else {
     // If we don't have a delegate, pass a copy of the current policies.
     scoped_ptr<PolicyBundle> bundle(new PolicyBundle());
     bundle->CopyFrom(policies());
     UpdatePolicy(bundle.Pass());
   }
 }
 
 }  // namespace policy