arc: enable Android tracing in verified-boot mode

chrome/browser/chromeos/trace/sys_trace_agent.cc

Index: chrome/browser/chromeos/trace/sys_trace_agent.cc
diff --git a/chrome/browser/chromeos/trace/sys_trace_agent.cc b/chrome/browser/chromeos/trace/sys_trace_agent.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b14a9b3db5f78700da8de26a5c5ed1f033fe3bea
--- /dev/null
+++ b/chrome/browser/chromeos/trace/sys_trace_agent.cc
@@ -0,0 +1,85 @@
+// Copyright 2016 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/chromeos/trace/sys_trace_agent.h"
+
+#include <string>

[Yusuke Sato, 2016/10/12 05:58:12]

you can remove this (see my comment below)

[shunhsingou, 2016/12/22 04:04:34]

Done.

+#include <utility>
+
+#include "base/logging.h"
+#include "base/memory/singleton.h"
+#include "base/trace_event/trace_event.h"

[Yusuke Sato, 2016/10/12 05:58:12]

same

[shunhsingou, 2016/12/22 04:04:34]

Done.

+#include "chromeos/dbus/dbus_thread_manager.h"
+#include "chromeos/dbus/debug_daemon_client.h"
+#include "components/arc/trace/arc_trace_bridge.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace chromeos {
+
+namespace {
+
+constexpr char kCrosTracingAgentName[] = "cros";
+constexpr char kCrosTraceLabel[] = "systemTraceEvents";
+
+}  // namespace
+
+std::string SysTraceAgent::GetTracingAgentName() {
+  return kCrosTracingAgentName;
+}
+
+std::string SysTraceAgent::GetTraceEventLabel() {
+  return kCrosTraceLabel;
+}
+
+void SysTraceAgent::StartAgentTracing(
+    const base::trace_event::TraceConfig& trace_config,
+    const StartAgentTracingCallback& callback) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  // Starts the system tracing on Chrome OS.
+  // The kernel level tracing is started by debugd via dbus, and the Android
+  // framework level tracing is started via mojo interface (ArcTraceBridge).
+  //
+  // Note that we bind mount /sys/kernel/debug/tracing/trace_marker into the
+  // container during initialization. Therefore, both tracing results will be
+  // collected by debugd from sysfs.
+  chromeos::DebugDaemonClient* debug_daemon =

[Yusuke Sato, 2016/10/12 05:58:12]

chromeos:: seems unnecessary (here and elsewhere)

[shunhsingou, 2016/12/22 04:04:34]

Done.

+      chromeos::DBusThreadManager::Get()->GetDebugDaemonClient();
+  // Starts kernel tracing via debugd.
+  if (!debug_daemon)
+    return;
+  debug_daemon->StartAgentTracing(trace_config, callback);
+  // Starts Android framework tracing via ArcTraceBridge.
+  auto* arc_trace_bridge = arc::ArcTraceBridge::Get();
+  if (!arc_trace_bridge)
+    return;

[Yusuke Sato, 2016/10/12 05:58:12]

This path is taken if the user who hasn't opted into ARC tries to use this
agent, and it's totally normal (hence no LOG()s), correct? If so, can you add
some code comments?

[shunhsingou, 2016/12/22 04:04:34]

Done.

+  arc_trace_bridge->StartTracing(trace_config);
+}
+
+void SysTraceAgent::StopAgentTracing(const StopAgentTracingCallback& callback) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  chromeos::DebugDaemonClient* debug_daemon =
+      chromeos::DBusThreadManager::Get()->GetDebugDaemonClient();
+  debug_daemon->StopAgentTracing(callback);
+
+  auto* arc_trace_bridge = arc::ArcTraceBridge::Get();
+  if (!arc_trace_bridge)
+    return
+  arc_trace_bridge->StopTracing();
+}
+
+void SysTraceAgent::SetStopAgentTracingTaskRunner(
+    scoped_refptr<base::TaskRunner> task_runner) {
+  chromeos::DebugDaemonClient* debug_daemon =
+      chromeos::DBusThreadManager::Get()->GetDebugDaemonClient();
+  debug_daemon->SetStopAgentTracingTaskRunner(task_runner);
+}
+
+SysTraceAgent* SysTraceAgent::GetInstance() {
+  return base::Singleton<SysTraceAgent>::get();
+}
+
+SysTraceAgent::SysTraceAgent() = default;
+SysTraceAgent::~SysTraceAgent() = default;
+
+}  // namespace chromeos