Add trace-to-file support for base::TestSuite

base/test/trace_to_file.cc

Index: base/test/trace_to_file.cc
diff --git a/base/test/trace_to_file.cc b/base/test/trace_to_file.cc
new file mode 100644
index 0000000000000000000000000000000000000000..6caaf47af32bbf3feedd17bce2a1e5af9272d500
--- /dev/null
+++ b/base/test/trace_to_file.cc
@@ -0,0 +1,104 @@
+// Copyright (c) 2014 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/trace_to_file.h"
+
+#include "base/base_switches.h"
+#include "base/command_line.h"
+#include "base/debug/trace_event_impl.h"
+#include "base/files/file_util.h"
+#include "base/run_loop.h"
+
+namespace base {
+namespace test {
+
+TraceToFile::TraceToFile() : started_(false) {
+}
+
+TraceToFile::~TraceToFile() {
+  EndTracingIfNeeded();
+}
+
+void TraceToFile::BeginTracingFromCommandLineOptions() {
+  DCHECK(CommandLine::InitializedForCurrentProcess());
+  DCHECK(!started_);
+
+  if (!CommandLine::ForCurrentProcess()->HasSwitch(switches::kTraceToFile))
+    return;
+
+  // Empty filter (i.e. just --trace-to-file) turns into default categories in
+  // TraceEventImpl
+  std::string filter = CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
+      switches::kTraceToFile);
+
+  FilePath path;
+  if (CommandLine::ForCurrentProcess()->HasSwitch(switches::kTraceToFileName)) {
+    path = FilePath(CommandLine::ForCurrentProcess()
+                        ->GetSwitchValuePath(switches::kTraceToFileName));
+  } else {
+    path = FilePath(FILE_PATH_LITERAL("trace.json"));
+  }
+
+  BeginTracing(path, filter);
+}
+
+void TraceToFile::BeginTracing(const FilePath& path,
+                               const std::string& categories) {
+  DCHECK(!started_);
+  started_ = true;
+  path_ = path;
+  WriteFileHeader();
+
+  debug::TraceLog::GetInstance()->SetEnabled(
+      debug::CategoryFilter(categories),
+      debug::TraceLog::RECORDING_MODE,
+      debug::TraceOptions(debug::RECORD_UNTIL_FULL));
+}
+
+void TraceToFile::WriteFileHeader() {
+  const char str[] = "{\"traceEvents\": [";
+  WriteFile(path_, str, static_cast<int>(strlen(str)));
+}
+
+void TraceToFile::AppendFileFooter() {
+  const char str[] = "]}";
+  AppendToFile(path_, str, static_cast<int>(strlen(str)));
+}
+
+void TraceToFile::TraceOutputCallback(const std::string& data) {
+  int ret = AppendToFile(path_, data.c_str(), static_cast<int>(data.size()));
+  DCHECK_NE(-1, ret);
+}
+
+static void OnTraceDataCollected(
+    Closure quit_closure,
+    debug::TraceResultBuffer* buffer,
+    const scoped_refptr<RefCountedString>& json_events_str,
+    bool has_more_events) {
+  buffer->AddFragment(json_events_str->data());
+  if (!has_more_events)
+    quit_closure.Run();
+}
+
+void TraceToFile::EndTracingIfNeeded() {
+  if (!started_)
+    return;
+  started_ = false;
+
+  debug::TraceLog::GetInstance()->SetDisabled();
+
+  debug::TraceResultBuffer buffer;
+  buffer.SetOutputCallback(
+      Bind(&TraceToFile::TraceOutputCallback, Unretained(this)));
+
+  RunLoop run_loop;
+  debug::TraceLog::GetInstance()->Flush(
+      Bind(&OnTraceDataCollected, run_loop.QuitClosure(), Unretained(&buffer)));
+  run_loop.Run();
+
+  AppendFileFooter();
+}
+
+}  // namespace test
+}  // namespace base