arc: enable Android tracing in verified-boot mode

chromeos/trace/arc_trace_agent.cc

+// 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 "chromeos/trace/arc_trace_agent.h"
+
+#include "base/bind.h"
+#include "base/logging.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/singleton.h"
+#include "base/threading/thread_task_runner_handle.h"
+
+namespace chromeos {
+
+namespace {
+
+constexpr char kArcTracingAgentName[] = "arc";
+constexpr char kArcTraceLabel[] = "ArcTraceEvents";
+
+class ArcTraceAgentImpl : public ArcTraceAgent {
+ public:
+  ArcTraceAgentImpl() : delegate_(nullptr), weak_ptr_factory_(this) {}
+
+  ~ArcTraceAgentImpl() override = default;
+
+  // base::trace_event::TracingAgent overrides:
+  std::string GetTracingAgentName() override { return kArcTracingAgentName; }
+
+  std::string GetTraceEventLabel() override { return kArcTraceLabel; }
+
+  void StartAgentTracing(const base::trace_event::TraceConfig& trace_config,

[Luis Héctor Chávez, 2017/01/17 19:20:32]

Can you add

DCHECK_CURRENTLY_ON(content::BrowserThread::UI);

on all methods? Otherwise the access to |delegate_| would be racy.

[Earl Ou, 2017/01/18 09:13:21]

Add thread_checker here as we don't want to add dependency to "content"

+                         const StartAgentTracingCallback& callback) override {
+    // delegate_ may be nullptr if ARC is not enabled on the system. In such
+    // case, simply do nothing.
+    if (!delegate_) {
+      // Use PostTask as the convention of TraceAgent. The caller expects
+      // callback to be called after this function returns.
+      base::ThreadTaskRunnerHandle::Get()->PostTask(
+          FROM_HERE, base::Bind(callback, GetTracingAgentName(), false));
+      return;
+    }
+
+    delegate_->StartTracing(trace_config,
+                            base::Bind(callback, GetTracingAgentName()));
+  }
+
+  void StopAgentTracing(const StopAgentTracingCallback& callback) override {
+    if (!delegate_) {
+      std::string no_data;
+      callback.Run(GetTracingAgentName(), GetTraceEventLabel(),
+                   base::RefCountedString::TakeString(&no_data));
+      return;
+    }
+
+    delegate_->StopTracing(base::Bind(&ArcTraceAgentImpl::OnStopAgentTracing,
+                                      weak_ptr_factory_.GetWeakPtr(),
+                                      callback));
+  }
+
+  // ArcTraceAgent overrides:
+  void SetDelegate(Delegate* delegate) override { delegate_ = delegate; }
+
+  static ArcTraceAgentImpl* GetInstance() {
+    return base::Singleton<ArcTraceAgentImpl>::get();
+  }
+
+ private:
+  // This allows constructor and destructor to be private and usable only

[Yusuke Sato, 2017/01/17 22:17:21]

Then can you make them private: ?

[Earl Ou, 2017/01/18 09:13:21]

Done.

+  // by the Singleton class.
+  friend struct base::DefaultSingletonTraits<ArcTraceAgentImpl>;
+
+  void OnStopAgentTracing(const StopAgentTracingCallback& callback,
+                          const std::string& report) {
+    std::string data(report);
+    callback.Run(kArcTracingAgentName, kArcTraceLabel,
+                 base::RefCountedString::TakeString(&data));
+  }
+
+  Delegate* delegate_;  // Owned by ArcServiceLauncher.
+  base::WeakPtrFactory<ArcTraceAgentImpl> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(ArcTraceAgentImpl);
+};
+
+}  // namespace
+
+// static
+ArcTraceAgent* ArcTraceAgent::GetInstance() {
+  return ArcTraceAgentImpl::GetInstance();
+}
+
+}  // namespace chromeos