Implements AddStartupEventsForTelemetry() in startup_metric_utils.cc for in-coming startup telemetry

components/startup_metric_utils/browser/startup_metric_utils.cc

 // Copyright 2013 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/startup_metric_utils/browser/startup_metric_utils.h"
 
 #include "base/containers/hash_tables.h"
 #include "base/environment.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
@@ skipping 266 matching lines @@
 
   base::TimeDelta browser_main_entry_time_raw_ms_high_word =
       base::TimeDelta::FromMilliseconds(
           (browser_main_entry_time_raw_ms >> 32) & kLowWordMask);
   // Shift by one because histograms only support non-negative values.
   base::TimeDelta browser_main_entry_time_raw_ms_low_word =
       base::TimeDelta::FromMilliseconds(
           (browser_main_entry_time_raw_ms >> 1) & kLower31BitsMask);
 
   // A timestamp is a 64 bit value, yet histograms can only store 32 bits.
+  // TODO(gabadie): Once startup_with_url.* benchmarks are replaced by
+  //    startup_with_url2.*, remove this dirty hack.
   LOCAL_HISTOGRAM_TIMES("Startup.BrowserMainEntryTimeAbsoluteHighWord",
       browser_main_entry_time_raw_ms_high_word);
   LOCAL_HISTOGRAM_TIMES("Startup.BrowserMainEntryTimeAbsoluteLowWord",
       browser_main_entry_time_raw_ms_low_word);
 }
 
 // Environment variable that stores the timestamp when the executable's main()
 // function was entered.
 const char kChromeMainTimeEnvVar[] = "CHROME_MAIN_TIME";
 
 // Returns the time of main entry recorded from RecordExeMainEntryTime.
 base::Time ExeMainEntryPointTime() {
   scoped_ptr<base::Environment> env(base::Environment::Create());
   std::string time_string;
   int64 time_int = 0;
   if (env->GetVar(kChromeMainTimeEnvVar, &time_string) &&
       base::StringToInt64(time_string, &time_int)) {
     return base::Time::FromInternalValue(time_int);
   }
   return base::Time();
 }
 
+// Traces process creation and main entry point mark events.
+void TraceMissingStartupInstantEvents() {

[gab, 2015/11/10 19:30:53]

Would prefer an even more specific name, e.g. AddStartupEventsForTelemetry().

With a description like:

// Records "instant" trace events for global timings observed by telemetry.


(if we ever need something more generic, we should add it to the macros in this
file, but for now a dedicated helper sgtm)

[gabadie, 2015/11/12 08:57:20]

Done.

+  static bool is_first_call = true;
+  if (!is_first_call)
+    return;
+  is_first_call = false;

[gab, 2015/11/10 19:30:53]

This method only be called once hence you shouldn't need to do this check.

[gabadie, 2015/11/12 08:57:20]

Good catch! Done.

+
+  DCHECK(!g_process_creation_time.Get().is_null());
+  DCHECK(!g_main_entry_point_time.Get().is_null());
+
+  TRACE_EVENT_INSTANT_WITH_TIMESTAMP("startup",

[gab, 2015/11/10 19:30:53]

Suggest running "git cl format", the argument alignment as-is is incorrect.

[gabadie, 2015/11/12 08:57:20]

My bad. Done.

+      "Startup.BrowserProcessCreation", 0,
+      StartupTimeToTimeTicks(g_process_creation_time.Get()).ToInternalValue());

[gab, 2015/11/10 19:30:53]

FYI: Very soon this should use g_process_creation_ticks instead (i.e. whenever
https://codereview.chromium.org/1425263003/ completes its journey through CQ).

[gabadie, 2015/11/12 08:57:20]

Done.

+
+  TRACE_EVENT_INSTANT_WITH_TIMESTAMP("startup",
+      "Startup.BrowserMainEntryPoint",  0,
+      StartupTimeToTimeTicks(g_main_entry_point_time.Get()).ToInternalValue());

[gab, 2015/11/10 19:30:53]

g_main_entry_point_ticks for this too

[gabadie, 2015/11/12 08:57:20]

Done.

+}
+
 }  // namespace
 
 bool WasNonBrowserUIDisplayed() {
   return g_non_browser_ui_displayed;
 }
 
 void SetNonBrowserUIDisplayed() {
   g_non_browser_ui_displayed = true;
 }
 
@@ skipping 10 matching lines @@
 }
 
 void RecordExeMainEntryPointTime(const base::Time& time) {
   std::string exe_load_time = base::Int64ToString(time.ToInternalValue());
   scoped_ptr<base::Environment> env(base::Environment::Create());
   env->SetVar(kChromeMainTimeEnvVar, exe_load_time);
 }
 
 void RecordBrowserMainMessageLoopStart(const base::Time& time,
                                        bool is_first_run) {
+  TraceMissingStartupInstantEvents();
   RecordHardFaultHistogram(is_first_run);
   RecordMainEntryTimeHistogram();
 
   const base::Time& process_creation_time = g_process_creation_time.Get();
   if (!is_first_run && !process_creation_time.is_null()) {
     UMA_HISTOGRAM_AND_TRACE_WITH_STARTUP_TEMPERATURE(
         UMA_HISTOGRAM_LONG_TIMES_100, "Startup.BrowserMessageLoopStartTime",
         process_creation_time, time);
   }
 
@@ skipping 149 matching lines @@
 
 base::Time MainEntryPointTime() {
   return g_main_entry_point_time.Get();
 }
 
 StartupTemperature GetStartupTemperature() {
   return g_startup_temperature;
 }
 
 }  // namespace startup_metric_utils