WIP: The tracing service prototype

services/resource_coordinator/public/cpp/tracing/chrome_agent.cc

Index: services/resource_coordinator/public/cpp/tracing/chrome_agent.cc
diff --git a/services/resource_coordinator/public/cpp/tracing/chrome_agent.cc b/services/resource_coordinator/public/cpp/tracing/chrome_agent.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b075335da516c1ed2dd14b944ebadb8e5810ecc5
--- /dev/null
+++ b/services/resource_coordinator/public/cpp/tracing/chrome_agent.cc
@@ -0,0 +1,96 @@
+// 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 "services/resource_coordinator/public/cpp/tracing/chrome_agent.h"
+
+#include "base/bind.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/ref_counted_memory.h"
+#include "base/trace_event/trace_log.h"
+#include "services/service_manager/public/cpp/connector.h"
+
+namespace resource_coordinator {
+namespace tracing {
+
+// static
+void ChromeAgent::InitializeIfNeeded(mojom::AgentSetPtr agent_set) {
+  static ChromeAgent* instance = nullptr;
+  if (!instance)
+    instance = new ChromeAgent(std::move(agent_set));
+}
+
+ChromeAgent::ChromeAgent(mojom::AgentSetPtr agent_set)
+    : agent_set_(std::move(agent_set)), binding_(this) {
+  agent_set_->RegisterAgent(binding_.CreateInterfacePtrAndBind(), "traceEvents",
+                            mojom::TraceDataType::ARRAY,
+                            false /* supports_explicit_clock_sync */);
+}
+
+ChromeAgent::~ChromeAgent() {}
+
+void ChromeAgent::StartTracing(const std::string& config,
+                               mojom::RecorderPtr recorder,
+                               bool report_categories_only,
+                               const StartTracingCallback& callback) {
+  DCHECK(!recorder_);
+  recorder_ = std::move(recorder);
+  report_categories_only_ = report_categories_only;
+  if (!base::trace_event::TraceLog::GetInstance()->IsEnabled()) {
+    base::trace_event::TraceLog::GetInstance()->SetEnabled(
+        base::trace_event::TraceConfig(config),
+        base::trace_event::TraceLog::RECORDING_MODE);
+  }
+  callback.Run();
+}
+
+void ChromeAgent::StopAndFlush() {
+  if (!recorder_)
+    return;
+  base::trace_event::TraceLog::GetInstance()->SetDisabled();
+  if (!report_categories_only_) {
+    base::trace_event::TraceLog::GetInstance()->Flush(
+        base::Bind(&ChromeAgent::SendChunk, base::Unretained(this)));
+  } else {
+    base::trace_event::TraceLog::GetInstance()->Flush(
+        base::trace_event::TraceLog::OutputCallback());
+    std::vector<std::string> category_vector;
+    base::trace_event::TraceLog::GetInstance()->GetKnownCategoryGroups(
+        &category_vector);
+    std::string categories_str;
+    bool first = true;
+    for (const auto& category : category_vector) {
+      if (!first)
+        categories_str += ",";
+      first = false;
+      categories_str += category;
+    }
+    recorder_->AddCategories(categories_str);
+    recorder_.reset();
+  }
+}
+
+void ChromeAgent::RequestClockSyncMarker(
+    const std::string& sync_id,
+    const RequestClockSyncMarkerCallback& callback) {
+  NOTREACHED() << "This agent does not support explicit clock sync";
+}
+
+void ChromeAgent::RequestBufferStatus(
+    const RequestBufferStatusCallback& callback) {
+  auto status = base::trace_event::TraceLog::GetInstance()->GetStatus();
+  callback.Run(status.event_capacity, status.event_count);
+}
+
+void ChromeAgent::SendChunk(
+    const scoped_refptr<base::RefCountedString>& events_str,
+    bool has_more_events) {
+  DCHECK(recorder_);
+  if (!events_str->data().empty())
+    recorder_->AddChunk(events_str->data());
+  if (!has_more_events)
+    recorder_.reset();
+}
+
+}  // namespace tracing
+}