Bug 901360 - (Part 5) Don't allow pausing downloads without partial data. r=margaret

--HG--
extra : rebase_source : c5455e3d650711692af3f97d90dd002845dcc669

mobile/android/chrome/content/aboutDownloads.js

@@ -53,7 +53,7 @@ let contextMenu = {
                             deleteDownload(download);
                           }),
       new ContextMenuItem("pause",
-                          download => !download.stopped,
+                          download => !download.stopped && download.hasPartialData,
                           download => download.cancel().then(null, Cu.reportError)),
       new ContextMenuItem("resume",
                           download => download.canceled && download.hasPartialData,

mobile/android/modules/DownloadNotifications.jsm

@@ -214,7 +214,9 @@ DownloadNotification.prototype = {
       if (this.download.currentBytes == 0) {
         this._updateOptionsForStatic(options, "alertDownloadsStart2");
       } else {
-        this._updateOptionsForOngoing(options, [kButtons.PAUSE, kButtons.CANCEL]);
+        let buttons = this.download.hasPartialData ? [kButtons.PAUSE, kButtons.CANCEL] :
+                                                     [kButtons.CANCEL]
+        this._updateOptionsForOngoing(options, buttons);
       }
     } else if (this._paused) {
       this._updateOptionsForOngoing(options, [kButtons.RESUME, kButtons.CANCEL]);