Added histograms to track duration when StartupTimeBomb goes off.

When StartupTimebomb goes off, collect the duration stats (difference
between when the timebomb went off and when it is started). We collect
this duration in terms of clock time, montonic clock time and thread CPU
time.

BUG=366699
R=jar@chromium.org

Review URL: https://codereview.chromium.org/273963002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@269602 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/metrics/thread_watcher.cc

@@ -910,13 +910,13 @@ class StartupWatchDogThread : public base::Watchdog {
     return;
 #else  // Android release: gather stats to figure out when to crash.
     // TODO(rtenneti): Delete this code, after getting data.
-    UMA_HISTOGRAM_TIMES("StartupTimebomm.Alarm.TimeDuration",
+    UMA_HISTOGRAM_TIMES("StartupTimeBomb.Alarm.TimeDuration",
                         base::Time::Now() - start_time_clock_);
-    UMA_HISTOGRAM_TIMES("StartupTimebomm.Alarm.TimeTicksDuration",
+    UMA_HISTOGRAM_TIMES("StartupTimeBomb.Alarm.TimeTicksDuration",
                         base::TimeTicks::Now() - start_time_monotonic_);
     if (base::TimeTicks::IsThreadNowSupported()) {
       UMA_HISTOGRAM_TIMES(
-          "StartupTimebomm.Alarm.ThreadNowDuration",
+          "StartupTimeBomb.Alarm.ThreadNowDuration",
           base::TimeTicks::ThreadNow() - start_time_thread_now_);
     }
     return;

tools/metrics/histograms/histograms.xml

@@ -26692,6 +26692,14 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="StartupTimeBomb.Alarm" units="milliseconds">
+  <owner>rtenneti@chromium.org</owner>
+  <summary>
+    Time duration measured from the time the startup timebomb was started and
+    when it went off.
+  </summary>
+</histogram>
+
 <histogram name="Suggestions.FailedRequestErrorCode" enum="NetErrorCodes">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>
@@ -45816,6 +45824,13 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <affected-histogram name="Net.SSL_Connection_Latency_Google"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="StartupTimeBombAlarm" separator=".">
+  <suffix name="ThreadNowDuration" label="Duration is in thread CPU time."/>
+  <suffix name="TimeDuration" label="Duration is in clock time."/>
+  <suffix name="TimeTicksDuration" label="Duration is in TimeTicks time."/>
+  <affected-histogram name="StartupTimeBomb.Alarm"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="SyzygyStartupTime">
   <suffix name="PreReadEnabled"/>
   <suffix name="PreReadDisabled"/>