Add Startup.SystemUptime histogram.

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 114 matching lines @@
     UMA_HISTOGRAM_WITH_STARTUP_TEMPERATURE(type, basename,                    \
                                            end_ticks - begin_ticks)           \
     TRACE_EVENT_ASYNC_BEGIN_WITH_TIMESTAMP1(                                  \
         "startup", basename, 0, begin_ticks.ToInternalValue(), "Temperature", \
         g_startup_temperature);                                               \
     TRACE_EVENT_ASYNC_END_WITH_TIMESTAMP1(                                    \
         "startup", basename, 0, end_ticks.ToInternalValue(), "Temperature",   \
         g_startup_temperature);                                               \
   }
 
+// Returns the time elapsed between system boot and process launch.
+base::TimeDelta GetStartupUptime() {

[gab, 2016/01/05 15:10:00]

GetSystemUptimeOnProcessLaunch() ?

[fdoray, 2016/01/05 15:34:01]

Done.

+  DCHECK(!g_process_creation_ticks.Get().is_null());
+  // base::SysInfo::Uptime returns the time elapsed between system boot and now.
+  // Substract the time elapsed between process launch and now to get the time
+  // elapsed between system boot and process launch.
+  return base::SysInfo::Uptime() -
+         (base::TimeTicks::Now() - g_process_creation_ticks.Get());
+}
+
+void RecordUptimeHistogram() {
+  UMA_HISTOGRAM_WITH_STARTUP_TEMPERATURE(UMA_HISTOGRAM_LONG_TIMES_100,
+                                         "Startup.Uptime", GetStartupUptime());

[gab, 2016/01/05 15:10:00]

"Startup.SystemUptime" ? (i.e. to make it clear it's the system's uptime)

[fdoray, 2016/01/05 15:34:01]

Done.

+}
+
 // On Windows, records the number of hard-faults that have occurred in the
 // current chrome.exe process since it was started. This is a nop on other
 // platforms.
 // crbug.com/476923
 // TODO(chrisha): If this proves useful, use it to split startup stats in two.
 void RecordHardFaultHistogram(bool is_first_run) {
 #if defined(OS_WIN)
   uint32_t hard_fault_count = 0;
 
   // Don't log a histogram value if unable to get the hard fault count.
@@ skipping 240 matching lines @@
   const std::string exe_load_ticks =
       base::Int64ToString(StartupTimeToTimeTicks(time).ToInternalValue());
   scoped_ptr<base::Environment> env(base::Environment::Create());
   env->SetVar(kChromeMainTicksEnvVar, exe_load_ticks);
 }
 
 void RecordBrowserMainMessageLoopStart(const base::TimeTicks& ticks,
                                        bool is_first_run) {
   AddStartupEventsForTelemetry();
   RecordHardFaultHistogram(is_first_run);
+  RecordUptimeHistogram();
   RecordMainEntryTimeHistogram();
 
   const base::TimeTicks& process_creation_ticks =
       g_process_creation_ticks.Get();
   if (!is_first_run && !process_creation_ticks.is_null()) {
     UMA_HISTOGRAM_AND_TRACE_WITH_STARTUP_TEMPERATURE(
         UMA_HISTOGRAM_LONG_TIMES_100, "Startup.BrowserMessageLoopStartTime",
         process_creation_ticks, ticks);
   }
 
@@ skipping 136 matching lines @@
 
 base::TimeTicks MainEntryPointTicks() {
   return g_browser_main_entry_point_ticks.Get();
 }
 
 StartupTemperature GetStartupTemperature() {
   return g_startup_temperature;
 }
 
 }  // namespace startup_metric_utils