Stop using [Client=...] feature of Mojom for BatteryMonitor

device/battery/battery_monitor_impl.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 "device/battery/battery_monitor_impl.h"
 
 #include "base/bind.h"
 
 namespace device {
 
 // static
 void BatteryMonitorImpl::Create(
     mojo::InterfaceRequest<BatteryMonitor> request) {
   new BatteryMonitorImpl(request.Pass());
 }
 
 BatteryMonitorImpl::BatteryMonitorImpl(
     mojo::InterfaceRequest<BatteryMonitor> request)
     : binding_(this, request.Pass()),
-      subscription_(BatteryStatusService::GetInstance()->AddCallback(
-          base::Bind(&BatteryMonitorImpl::DidChange, base::Unretained(this)))) {
+      status_to_report_(false) {
+  // NOTE: DidChange may be called before AddCallback returns. This is done to
+  // report current status.
+  subscription_ = BatteryStatusService::GetInstance()->AddCallback(
+      base::Bind(&BatteryMonitorImpl::DidChange, base::Unretained(this)));
 }
 
 BatteryMonitorImpl::~BatteryMonitorImpl() {
 }
 
+void BatteryMonitorImpl::QueryNextStatus(
+    const BatteryStatusCallback& callback) {
+  callbacks_.push_back(callback);
+
+  if (status_to_report_)
+    ReportStatus();
+}
+
 void BatteryMonitorImpl::RegisterSubscription() {
 }
 
 void BatteryMonitorImpl::DidChange(const BatteryStatus& battery_status) {
-  BatteryStatusPtr status(BatteryStatus::New());
-  *status = battery_status;
-  binding_.client()->DidChange(status.Pass());
+  status_ = battery_status;
+  status_to_report_ = true;
+
+  if (!callbacks_.empty())
+    ReportStatus();
+}
+
+void BatteryMonitorImpl::ReportStatus() {
+  for (const auto& callback : callbacks_)
+    callback.Run(status_.Clone());
+  callbacks_.clear();
+
+  status_to_report_ = false;
 }
 
 }  // namespace device