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

content/browser/browser_main_loop.cc

Index: content/browser/browser_main_loop.cc
diff --git a/content/browser/browser_main_loop.cc b/content/browser/browser_main_loop.cc
index b5159df02a3e91b640f71dc37d0e5e82f77e634a..df19ee86f070e4da101a1a94f7167b9a1cd9390f 100644
--- a/content/browser/browser_main_loop.cc
+++ b/content/browser/browser_main_loop.cc
@@ -26,6 +26,7 @@
 #include "base/timer/hi_res_timer_manager.h"
 #include "base/trace_event/memory_dump_manager.h"
 #include "base/trace_event/trace_event.h"
+#include "components/tracing/trace_config_file.h"
 #include "components/tracing/tracing_switches.h"
 #include "content/browser/browser_thread_impl.h"
 #include "content/browser/device_sensors/device_inertial_sensor_service.h"
@@ -390,9 +391,11 @@ BrowserMainLoop::BrowserMainLoop(const MainFunctionParams& parameters)
       result_code_(RESULT_CODE_NORMAL_EXIT),
       created_threads_(false),
       // ContentMainRunner should have enabled tracing of the browser process

[no sievers, 2015/08/24 22:50:16]

If so, can we simply do:
DCHECK_IMPLIES(parameters.command_line.HasSwitch(switches::kTraceStartup),
tracing::TraceLog::IsEnabled());

or should it be TracingController::GetInstance()->IsRecording()?

[Zhen Wang, 2015/08/25 17:38:14]

I am not aware of any other ways lead to tracing being enabled here. But I think
it is safe to check the flags, because we other ways may be added in the future.
And |_is_tracing_startup_for_duration_| is specific to those two flags, but not
to tracing controller.

-      // when kTraceStartup is in the command line.
-      is_tracing_startup_(
-          parameters.command_line.HasSwitch(switches::kTraceStartup)) {
+      // when kTraceStartup or kTraceConfigFile is in the command line.
+      is_tracing_startup_for_duration_(
+          parameters.command_line.HasSwitch(switches::kTraceStartup) ||
+          (tracing::TraceConfigFile::GetInstance()->IsEnabled() &&
+           tracing::TraceConfigFile::GetInstance()->GetStartupDuration() > 0)) {

[no sievers, 2015/08/24 22:50:16]

Are there other ways than the two command lines (config or kTraceStartup) that
would lead to tracing being enabled here? If not can we just have a single check
whether it's enabled?

[Zhen Wang, 2015/08/25 17:38:14]

ditto

   DCHECK(!g_current_browser_main_loop);
   g_current_browser_main_loop = this;
 }
@@ -578,9 +581,9 @@ void BrowserMainLoop::PostMainMessageLoopStart() {
   // Start tracing to a file if needed. Only do this after starting the main
   // message loop to avoid calling MessagePumpForUI::ScheduleWork() before
   // MessagePumpForUI::Start() as it will crash the browser.
-  if (is_tracing_startup_) {
-    TRACE_EVENT0("startup", "BrowserMainLoop::InitStartupTracing");
-    InitStartupTracing(parsed_command_line_);
+  if (is_tracing_startup_for_duration_) {
+    TRACE_EVENT0("startup", "BrowserMainLoop::InitStartupTracingForDuration");
+    InitStartupTracingForDuration(parsed_command_line_);
   }
 #endif  // !defined(OS_IOS)
 
@@ -1316,39 +1319,52 @@ void BrowserMainLoop::MainMessageLoopRun() {
 
 base::FilePath BrowserMainLoop::GetStartupTraceFileName(
     const base::CommandLine& command_line) const {
-  base::FilePath trace_file = command_line.GetSwitchValuePath(
-      switches::kTraceStartupFile);
-  // trace_file = "none" means that startup events will show up for the next
-  // begin/end tracing (via about:tracing or AutomationProxy::BeginTracing/
-  // EndTracing, for example).
-  if (trace_file == base::FilePath().AppendASCII("none"))
-    return trace_file;
-
-  if (trace_file.empty()) {
+  base::FilePath trace_file;
+  if (command_line.HasSwitch(switches::kTraceStartup)) {
+    trace_file = command_line.GetSwitchValuePath(
+        switches::kTraceStartupFile);
+    // trace_file = "none" means that startup events will show up for the next
+    // begin/end tracing (via about:tracing or AutomationProxy::BeginTracing/
+    // EndTracing, for example).
+    if (trace_file == base::FilePath().AppendASCII("none"))
+      return trace_file;
+
+    if (trace_file.empty()) {
+#if defined(OS_ANDROID)
+      TracingControllerAndroid::GenerateTracingFilePath(&trace_file);
+#else
+      // Default to saving the startup trace into the current dir.
+      trace_file = base::FilePath().AppendASCII("chrometrace.log");
+#endif
+    }
+  } else {
 #if defined(OS_ANDROID)
     TracingControllerAndroid::GenerateTracingFilePath(&trace_file);
 #else
-    // Default to saving the startup trace into the current dir.
-    trace_file = base::FilePath().AppendASCII("chrometrace.log");
+    trace_file = tracing::TraceConfigFile::GetInstance()->GetResultFile();
 #endif
   }
 
   return trace_file;
 }
 
-void BrowserMainLoop::InitStartupTracing(
+void BrowserMainLoop::InitStartupTracingForDuration(
     const base::CommandLine& command_line) {
-  DCHECK(is_tracing_startup_);
+  DCHECK(is_tracing_startup_for_duration_);
 
   startup_trace_file_ = GetStartupTraceFileName(parsed_command_line_);
 
-  std::string delay_str = command_line.GetSwitchValueASCII(
-      switches::kTraceStartupDuration);
   int delay_secs = 5;
-  if (!delay_str.empty() && !base::StringToInt(delay_str, &delay_secs)) {
-    DLOG(WARNING) << "Could not parse --" << switches::kTraceStartupDuration
-        << "=" << delay_str << " defaulting to 5 (secs)";
-    delay_secs = 5;
+  if (command_line.HasSwitch(switches::kTraceStartup)) {
+    std::string delay_str = command_line.GetSwitchValueASCII(
+        switches::kTraceStartupDuration);
+    if (!delay_str.empty() && !base::StringToInt(delay_str, &delay_secs)) {
+      DLOG(WARNING) << "Could not parse --" << switches::kTraceStartupDuration
+          << "=" << delay_str << " defaulting to 5 (secs)";
+      delay_secs = 5;
+    }
+  } else {
+    delay_secs = tracing::TraceConfigFile::GetInstance()->GetStartupDuration();
   }
 
   startup_trace_timer_.Start(FROM_HERE,
@@ -1358,9 +1374,9 @@ void BrowserMainLoop::InitStartupTracing(
 }
 
 void BrowserMainLoop::EndStartupTracing() {
-  DCHECK(is_tracing_startup_);
+  DCHECK(is_tracing_startup_for_duration_);
 
-  is_tracing_startup_ = false;
+  is_tracing_startup_for_duration_ = false;
   TracingController::GetInstance()->DisableRecording(
       TracingController::CreateFileSink(
           startup_trace_file_,