Relanding this as this did not fix the chromiumos breakage.

chrome/browser/policy/cloud_policy_client.cc

Index: chrome/browser/policy/cloud_policy_client.cc
===================================================================
--- chrome/browser/policy/cloud_policy_client.cc	(revision 150399)
+++ chrome/browser/policy/cloud_policy_client.cc	(working copy)
@@ -31,9 +31,10 @@
       submit_machine_id_(false),
       public_key_version_(-1),
       public_key_version_valid_(false),
-      service_(service),
-      status_provider_(status_provider),
-      status_(DM_STATUS_SUCCESS) {}
+      service_(service),                  // Can be NULL for unit tests.
+      status_provider_(status_provider),  // Can be NULL for unit tests.
+      status_(DM_STATUS_SUCCESS) {
+}
 
 CloudPolicyClient::~CloudPolicyClient() {}
 
@@ -52,6 +53,7 @@
 }
 
 void CloudPolicyClient::Register(const std::string& auth_token) {
+  DCHECK(service_);
   DCHECK(!auth_token.empty());
   DCHECK(!is_registered());
 
@@ -120,6 +122,7 @@
 }
 
 void CloudPolicyClient::Unregister() {
+  DCHECK(service_);
   request_job_.reset(
       service_->CreateJob(DeviceManagementRequestJob::TYPE_UNREGISTRATION));
   request_job_->SetDMToken(dm_token_);