[Chromoting] Retrieve process resource usage (ProcessStats) and its tests

remoting/host/host_stats.cc

+// Copyright 2017 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 "base/bind.h"
+#include "base/location.h"
+#include "base/logging.h"
+#include "base/message_loop/message_loop.h"
+#include "remoting/host/host_stats.h"
+
+namespace remoting {
+namespace host {
+
+HostStats::HostStats(HostStatsStub* host_stats_stub, base::TimeDelta interval)
+    : host_stats_stub_(host_stats_stub),
+      interval_(interval),
+      metrics_(base::ProcessMetrics::CreateCurrentProcessMetrics()),
+      weak_factory_(this) {
+  DCHECK(host_stats_stub_);
+  DCHECK(!interval_.is_zero());
+
+  PostTask();
+}
+
+HostStats::~HostStats() = default;
+
+void HostStats::PostTask() {
+  base::MessageLoop::current()->task_runner()->PostDelayedTask(FROM_HERE,

[Sergey Ulanov, 2017/03/27 19:43:20]

I think it would be better to use base::RepeatingTimer here.

Otherwise please use ThreadTaskRunnerHandle::Get() instead of
base::MessageLoop::current()->task_runner()

[Hzj_jie, 2017/03/30 01:09:45]

Done.

+      base::Bind(&HostStats::ReportUsage, weak_factory_.GetWeakPtr()),
+      interval_);
+}
+
+void HostStats::ReportUsage() {
+  ProcessResourceUsage current;
+  current.processor_usage = metrics_->GetPlatformIndependentCPUUsage();
+  current.working_set_size = metrics_->GetWorkingSetSize();
+  current.pagefile_size = metrics_->GetPagefileUsage();
+  {
+    base::AutoLock lock(lock_);

[Sergey Ulanov, 2017/03/27 19:43:20]

Why do we need lock?

[Hzj_jie, 2017/03/30 01:09:45]

I suppose HostStats::OnHostStats() should be called by
DesktopSessionProxy::OnMessageReceived(), which is in network thread. But this
class should be generated in ClientSession::OnConnectionAuthenticated(), which I
have not found a very clear information which thread it belongs to. So they may
belong to different threads. Posting task seems over-kill to me, considering it
copies only several small fields.

If we can confirm the ClientSession::OnConnectionAuthenticated() is also
executed in network thread. We can also replace this lock with a thread-checker.

+    current.Append(received_usage_);
+  }
+  host_stats_stub_->OnHostStats(current);
+
+  PostTask();
+}
+
+void HostStats::OnHostStats(const ProcessResourceUsage& usage) {
+  base::AutoLock lock(lock_);
+  received_usage_ = usage;
+}
+
+}  // namespace host
+}  // namespace remoting