Fix for bug 98476. Add safe save & redundant backup support for prefs.js. r=sfraser, sr=alecf.

suite/common/pref/nsPrefWindow.js

@@ -254,7 +254,26 @@ nsPrefWindow.prototype =
                   }
               }
               }
-              this.pref.savePrefFile(null);
+              try 
+                {
+                  this.pref.savePrefFile(null);
+                }
+              catch (e)
+                {
+                  try
+                    {
+                      var prefUtilBundle = document.getElementById("bundle_prefutilities");
+                      var alertText = prefUtilBundle.getString("prefSaveFailedAlert");
+                      var titleText = prefUtilBundle.getString("prefSaveFailedTitle");
+                      var promptService = Components.classes["@mozilla.org/embedcomp/prompt-service;1"]
+                                                    .getService(Components.interfaces.nsIPromptService);
+                      promptService.alert(window, titleText, alertText);
+                    }
+                  catch (e)
+                    {
+                      dump(e + "\n");
+                    }
+                }
           },                        
 
       switchPage:

suite/common/pref/pref.xul

@@ -60,6 +60,8 @@
   
   </script>        
         
+  <stringbundle id="bundle_prefutilities"
+               src="chrome://communicator/locale/pref/prefutilities.properties"/>
   <script type="application/x-javascript" src="chrome://global/content/nsWidgetStateManager.js"/>
   <script type="application/x-javascript" src="chrome://communicator/content/pref/nsPrefWindow.js"/>
   <script type="application/x-javascript" src="chrome://communicator/content/pref/pref-help.js"/>

suite/locales/en-US/chrome/common/pref/prefutilities.properties

@@ -15,3 +15,5 @@ oldTheme=You have selected a theme which was designed for an earlier version of
 languageAlert=Please restart %brand% to use the new preferred language or region setting.
 languageTitle=Change Language
 
+prefSaveFailedAlert=Failed to save the preferences file. Any preference changes will be lost at the end of this session.
+prefSaveFailedTitle=Save Error