Bug 1185927 - Don't show extra dialog when user cancels add-on download. r=sebastian

--HG--
extra : commitid : J8UG43A1wQy
extra : rebase_source : ea32433c55854275de6615ca88ab068a74168c93

mobile/android/chrome/content/browser.js

@@ -6214,9 +6214,7 @@ var XPInstallObserver = {
     this._showErrorMessage(aInstall);
   },
 
-  onDownloadCancelled: function(aInstall) {
-    this._showErrorMessage(aInstall);
-  },
+  onDownloadCancelled: function(aInstall) {},
 
   _showErrorMessage: function(aInstall) {
     // Don't create a notification for distribution add-ons.