Add UMA to measure NPEs coming from Android Wifi/Connectivity services

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 dc74f51c363ee8d8c3eb01bd89ff4f7c64b95009..858183480384acad03a05b6e55fa0e00619359f5 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -25330,6 +25330,42 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="NCN.getNetInfo1stSuccess" enum="BooleanSuccess">

[Ilya Sherman, 2016/06/14 21:50:44]

(Just within histograms.xml), please use a custom enum with labels like "Had
NullPointerException" and "No exception"

[pauljensen, 2016/06/15 11:22:54]

Done.

+  <owner>pauljensen@chromium.org</owner>
+  <summary>
+    True if the first call to ConnectivityManager.getNetworkInfo(Network) did
+    not throw NullPointerException, false if it did.
+  </summary>
+</histogram>
+
+<histogram name="NCN.getNetInfo2ndSuccess" enum="BooleanSuccess">
+  <owner>pauljensen@chromium.org</owner>
+  <summary>
+    Recorded after the first call to ConnectivityManager.getNetworkInfo(Network)
+    threw a NullPointerException. True if the second call to
+    ConnectivityManager.getNetworkInfo(Network) did not throw
+    NullPointerException, false if it did.
+  </summary>
+</histogram>
+
+<histogram name="NCN.getWifiInfo1stSuccess" enum="BooleanSuccess">
+  <owner>pauljensen@chromium.org</owner>
+  <summary>
+    True if the first call to WifiManager.getConnectionInfo() did not throw
+    NullPointerException, false if it did.
+  </summary>
+</histogram>
+
+<histogram name="NCN.getWifiInfo2ndSuccess" enum="BooleanSuccess">
+  <owner>pauljensen@chromium.org</owner>
+  <summary>
+    Recorded after the first call to WifiManager.getConnectionInfo() threw a
+    NullPointerException. True if the second call to
+    ConnectivityManager.getNetworkInfo(Network) did not throw
+    NullPointerException, false if it did.

[Ilya Sherman, 2016/06/14 21:50:45]

For all of these histograms, I think it would be helpful to provide a bit of
context -- perhaps just a bug link -- explaining *why* this is a useful thing to
measure.

[pauljensen, 2016/06/15 11:22:54]

Done.

+  </summary>
+</histogram>
+
 <histogram name="NCN.IPAddressChange" units="ms">
   <owner>pauljensen@chromium.org</owner>
   <summary>Time between IP address change messages.</summary>