Bug 981028 - Part 2: Probe for setting a default panel. r=liuche

mobile/android/base/TelemetryContract.java

@@ -26,6 +26,9 @@ public interface TelemetryContract {
 
         // Top site edited.
         public static final String TOP_SITES_EDIT = "edit.1";
+
+        // Set default panel.
+        public static final String PANEL_SET_DEFAULT = "setdefault.1";
     }
 
     /**

mobile/android/base/preferences/PanelsPreferenceCategory.java

@@ -4,6 +4,8 @@
 
 package org.mozilla.gecko.preferences;
 
+import org.mozilla.gecko.Telemetry;
+import org.mozilla.gecko.TelemetryContract;
 import org.mozilla.gecko.home.HomeConfig;
 import org.mozilla.gecko.home.HomeConfig.PanelConfig;
 import org.mozilla.gecko.home.HomeConfig.State;
@@ -170,6 +172,8 @@ public class PanelsPreferenceCategory extends CustomListCategory {
 
         mConfigEditor.setDefault(id);
         mConfigEditor.apply();
+
+        Telemetry.sendUIEvent(TelemetryContract.Event.PANEL_SET_DEFAULT, null, id);
     }
 
     @Override