Add basic tracing support to the gtest launcher

base/test/launcher/test_launcher_tracer.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 "base/test/launcher/test_launcher_tracer.h"
+
+#include "base/json/json_file_value_serializer.h"
+#include "base/strings/stringprintf.h"
+#include "base/values.h"
+
+namespace base {
+
+TestLauncherTracer::TestLauncherTracer()
+    : trace_start_time_(TimeTicks::Now()) {}
+
+TestLauncherTracer::~TestLauncherTracer() {}
+
+void TestLauncherTracer::RecordProcessExecution(TimeTicks start_time,
+                                                TimeDelta duration) {
+  AutoLock lock(lock_);
+
+  Event event;
+  event.name = StringPrintf("process #%zu", events_.size());
+  event.timestamp = start_time;
+  event.duration = duration;
+  event.thread_id = PlatformThread::CurrentId();
+  events_.push_back(event);
+}
+
+bool TestLauncherTracer::Dump(const FilePath& path) {
+  AutoLock lock(lock_);
+
+  std::unique_ptr<ListValue> json_events(new ListValue);
+  for (const Event& event : events_) {
+    std::unique_ptr<DictionaryValue> json_event(new DictionaryValue);
+    json_event->SetString("name", event.name);
+    json_event->SetString("ph", "X");
+    json_event->SetInteger(
+        "ts", (event.timestamp - trace_start_time_).InMicroseconds());
+    json_event->SetInteger("dur", event.duration.InMicroseconds());
+    json_event->SetInteger("tid", event.thread_id);
+
+    // Add fake values required by the trace viewer.
+    json_event->SetInteger("pid", 0);
+
+    json_events->Append(std::move(json_event));
+  }
+
+  JSONFileValueSerializer serializer(path);
+  return serializer.Serialize(*json_events);
+}
+
+}  // namespace base