apps: add DisconnectReason to netlog summary

Shill now processes DisconnectReason property updates from supplicant.
These log lines will now be highlighted in the shill log processor.

Sample line from log:
[2015-07-14T20:35:50.708693+00:00] [94:16:21.598] WiFi wlan0 supplicant
updated DisconnectReason -4

The log line will appear in the manager summary and will be highlighted
in the log text.

BUG=chromium:510182
TEST=checked manually and ran "grunt test"

Change-Id: I39e78e725319fe79d6f83ed35e7c9701f2c92d9c
diff --git a/netlog_summary.js b/netlog_summary.js
index 0ca5646..4f8959f 100644
--- a/netlog_summary.js
+++ b/netlog_summary.js
@@ -373,6 +373,16 @@
               result[1]);
       return 'basic';
     }
+  },
+  'disconnect_reason': {
+    re: /\] (.*DisconnectReason (-?\d*)(?: was )?(-?\d*))/,
+    handler: function(processingState, result) {
+      // new reason code at result[2] old reason (if applicable) result[3]
+      addNote(processingState.currentManager,
+              processingState.time[0],
+              result[1]);
+      return 'basic';
+    }
   }
 };