Add JobController/Job count to UMA histograms when the count hits limit

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 573a82fc85f79fa58b750b1d80785fba34266952..e696a9d88faa53492bb5376356062c4243dc20d6 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -34687,22 +34687,35 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Net.JobControllerSet.CountOfJobController"
+    units="job_controllers">
+  <owner>zhongyi@chromium.org</owner>
+  <summary>
+    This counts number of all the uncleaned job controllers when it hits limit

[xunjieli, 2017/04/10 23:13:21]

nit: consider replace "uncleaned."  I haven't seen it used as a verb.


One suggestion:
This reports the number of live job controllers when that number is a multiple
of 100.

[Zhongyi Shi, 2017/04/10 23:30:12]

Done.

+    of 200, 400, 800, etc.
+  </summary>
+</histogram>
+
+<histogram name="Net.JobControllerSet.CountOfJobControllerAtShutDown"
+    units="job_controllers">
+  <owner>zhongyi@chromium.org</owner>
+  <summary>
+    This counts number of all the uncleaned job controllers that are sill alive.

[xunjieli, 2017/04/10 23:13:21]

nit:  there is a typo in this sentence.
Could get rid of the word "uncleaned"

[Zhongyi Shi, 2017/04/10 23:30:12]

Done.

+  </summary>
+</histogram>
+
 <histogram name="Net.JobControllerSet.CountOfNonPreconnectAltJob"
     units="alt_jobs">
   <owner>zhongyi@chromium.org</owner>
   <summary>
-    This counts number of alternative jobs which are still alive when
-    HttpStreamFactory is destructed.
+    This counts number of alternative jobs which are still alive.
   </summary>
 </histogram>
 
 <histogram name="Net.JobControllerSet.CountOfNonPreconnectMainJob"
     units="main_jobs">
   <owner>zhongyi@chromium.org</owner>
-  <summary>
-    This counts number of main jobs which are still alive when HttpStreamFactory
-    is destructed.
-  </summary>
+  <summary>This counts number of main jobs which are still alive.</summary>
 </histogram>
 
 <histogram name="Net.JobControllerSet.CountOfPreconnect"
@@ -34710,7 +34723,7 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <owner>zhongyi@chromium.org</owner>
   <summary>
     This counts number of job controllers which are used for preconnect and are
-    still alive when HttpStreamFactory is destructed.
+    still alive.
   </summary>
 </histogram>