[Startup Tracing] Add --trace-config-file flag

components/tracing/trace_config_file.cc

Index: components/tracing/trace_config_file.cc
diff --git a/components/tracing/trace_config_file.cc b/components/tracing/trace_config_file.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e1cbc5c391e6c98edda8f907a91c53e9d39b7e81
--- /dev/null
+++ b/components/tracing/trace_config_file.cc
@@ -0,0 +1,140 @@
+// Copyright (c) 2015 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 "components/tracing/trace_config_file.h"
+
+#include <string>
+
+#include "base/command_line.h"
+#include "base/files/file_util.h"
+#include "base/json/json_reader.h"
+#include "base/json/json_writer.h"
+#include "base/logging.h"
+#include "base/memory/singleton.h"
+#include "base/values.h"
+#include "components/tracing/tracing_switches.h"
+
+namespace tracing {
+
+namespace {
+
+// Maximum trace config file size that will be loaded, in bytes.
+const size_t kTraceConfigFileSizeLimit = 64 * 1024;
+
+// Trace config file path:
+// - Android: /data/local/chrome-trace-config.json
+// - Others: specified by --trace-config-file flag.
+#if defined(OS_ANDROID)
+const base::FilePath::CharType kAndroidTraceConfigFile[] =
+    FILE_PATH_LITERAL("/data/local/chrome-trace-config.json");
+#endif
+
+const base::FilePath::CharType kDefaultResultFile[] =
+    FILE_PATH_LITERAL("chrometrace.log");
+
+// String parameters that can be used to parse the trace config file content.
+const char kTraceConfigParam[] = "trace_config";
+const char kStartupDurationParam[] = "startup_duration";
+const char kResultFileParam[] = "result_file";
+
+} // namespace
+
+TraceConfigFile* TraceConfigFile::GetInstance() {
+  return Singleton<TraceConfigFile,
+                   DefaultSingletonTraits<TraceConfigFile>>::get();
+}
+
+TraceConfigFile::TraceConfigFile()
+    : is_enabled_(false),
+      trace_config_(base::trace_event::TraceConfig()),
+      startup_duration_(0),
+      result_file_(kDefaultResultFile) {
+#if defined(OS_ANDROID)
+  base::FilePath trace_config_file(kAndroidTraceConfigFile);
+#else
+  const base::CommandLine& command_line =
+      *base::CommandLine::ForCurrentProcess();
+  if (!command_line.HasSwitch(switches::kTraceConfigFile) ||
+      command_line.HasSwitch(switches::kTraceStartup) ||
+      command_line.HasSwitch(switches::kTraceShutdown)) {
+    return;
+  }
+  base::FilePath trace_config_file =
+      command_line.GetSwitchValuePath(switches::kTraceConfigFile);
+#endif
+
+  if (trace_config_file.empty()) {
+    // If the trace config file path is not specified, trace Chrome with the
+    // default configuration for 5 sec.
+    startup_duration_ = 5;
+    is_enabled_ = true;
+    return;
+  }
+
+  if (!base::PathExists(trace_config_file))
+    return;
+
+  std::string trace_config_file_content;
+  if (!base::ReadFileToString(trace_config_file,
+                              &trace_config_file_content,
+                              kTraceConfigFileSizeLimit)) {
+    return;
+  }
+  is_enabled_ = ParseTraceConfigFileContent(trace_config_file_content);
+}
+
+TraceConfigFile::~TraceConfigFile() {
+}
+
+bool TraceConfigFile::ParseTraceConfigFileContent(std::string content) {
+  scoped_ptr<base::Value> value(base::JSONReader::Read(content));
+  if (!value || !value->IsType(base::Value::TYPE_DICTIONARY))
+    return false;
+
+  scoped_ptr<base::DictionaryValue> dict(
+      static_cast<base::DictionaryValue*>(value.release()));
+
+  base::DictionaryValue* trace_config_dict = NULL;
+  if (!dict->GetDictionary(kTraceConfigParam, &trace_config_dict))
+    return false;
+
+  std::string trace_config_str;
+  base::JSONWriter::Write(*trace_config_dict, &trace_config_str);
+  trace_config_ = base::trace_event::TraceConfig(trace_config_str);
+
+  if (!dict->GetInteger(kStartupDurationParam, &startup_duration_))
+      startup_duration_ = 0;
+
+  if (startup_duration_ < 0)
+      startup_duration_ = 0;
+
+  std::string result_file_str;
+  if (dict->GetString(kResultFileParam, &result_file_str))
+    result_file_ = base::FilePath().AppendASCII(result_file_str);
+
+  return true;
+}
+
+bool TraceConfigFile::IsEnabled() const {
+  return is_enabled_;
+}
+
+base::trace_event::TraceConfig TraceConfigFile::GetTraceConfig() const {
+  DCHECK(IsEnabled());
+  return trace_config_;
+}
+
+int TraceConfigFile::GetStartupDuration() const {
+  DCHECK(IsEnabled());
+  return startup_duration_;
+}
+
+#if !defined(OS_ANDROID)
+base::FilePath TraceConfigFile::GetResultFile() const {
+  DCHECK(IsEnabled());
+  return result_file_;
+}
+#endif
+
+}  // namespace tracing