From fca0d639fbcd0c30169c80261781005510390d09 Mon Sep 17 00:00:00 2001
From: Edgar Chen <echen@mozilla.com>
Date: Fri, 31 Oct 2014 15:15:47 +0800
Subject: [PATCH] Bug 1092013 - Part 1: mozMobileConnection.data.cell is reset
 to `null` unexpectedly in MobileConnectionService. r=hsinyi

---
 .../gonk/MobileConnectionService.js           | 24 +++++++++++++------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/dom/mobileconnection/gonk/MobileConnectionService.js b/dom/mobileconnection/gonk/MobileConnectionService.js
index 962bc05a187..cdc3bdfa713 100644
--- a/dom/mobileconnection/gonk/MobileConnectionService.js
+++ b/dom/mobileconnection/gonk/MobileConnectionService.js
@@ -478,6 +478,12 @@ MobileConnectionProvider.prototype = {
     return true;
   },
 
+  /**
+   * The design of this updating function is to update the attribute in
+   * |aDestInfo| *only if* new data (e.g. aSrcInfo) contains the same attribute.
+   * Thus, for the attribute in |aDestInfo| that isn't showed in |aSrcInfo|, it
+   * should just keep the original value unchanged.
+   */
   _updateConnectionInfo: function(aDestInfo, aSrcInfo) {
     let isUpdated = false;
     for (let key in aSrcInfo) {
@@ -502,15 +508,13 @@ MobileConnectionProvider.prototype = {
     } else {
       aDestInfo.network = this._operatorInfo;
 
-      if (aSrcInfo.cell == null) {
-        if (aDestInfo.cell != null) {
-          isUpdated = true;
-          aDestInfo.cell = null;
-        }
-      } else {
-        if (aDestInfo.cell == null) {
+      // If no new cell data is passed, we should just keep the original cell
+      // data unchanged.
+      if (aSrcInfo.cell) {
+        if (!aDestInfo.cell) {
           aDestInfo.cell = new MobileCellInfo();
         }
+
         isUpdated = this._updateInfo(aDestInfo.cell, aSrcInfo.cell) || isUpdated;
       }
     }
@@ -520,6 +524,12 @@ MobileConnectionProvider.prototype = {
     return isUpdated;
   },
 
+  /**
+   * The design of this updating function is to update the attribute in
+   * |aDestInfo| *only if* new data (e.g. aSrcInfo) contains the same attribute.
+   * Thus, for the attribute in |aDestInfo| that isn't showed in |aSrcInfo|, it
+   * should just keep the original value unchanged.
+   */
   _updateInfo: function(aDestInfo, aSrcInfo) {
     let isUpdated = false;
     for (let key in aSrcInfo) {