Bug 1544834 - Replace non-test uses of deprecated Array generics r=evilpie,dao

- `Array.forEach` becomes for-of loop or `array.forEach`.
- `Array.slice(a)` or `Array.slice(a, 0)` becomes `Array.from(a)`.
- `Array.map` becomes `Array.from`
- `Array` copy + concatenation becomes Array literal + spread syntax.
- All other `Array.X(a, ...)` become `Array.prototype.X.call` or `Array.from(a).X(...)`

Differential Revision: https://phabricator.services.mozilla.com/D27802

browser/components/downloads/content/allDownloadsView.js

@@ -295,8 +295,9 @@ DownloadsPlacesView.prototype = {
   },
 
   get selectedNodes() {
-      return Array.filter(this._richlistbox.selectedItems,
-                          element => element._shell.download.placesNode);
+    return Array.prototype.filter.call(
+      this._richlistbox.selectedItems,
+      element => element._shell.download.placesNode);
   },
 
   get selectedNode() {
@@ -501,14 +502,15 @@ DownloadsPlacesView.prototype = {
       case "downloadsCmd_clearDownloads":
         return this.canClearDownloads(this._richlistbox);
       default:
-        return Array.every(this._richlistbox.selectedItems,
-                           element => element._shell.isCommandEnabled(aCommand));
+        return Array.prototype.every.call(
+          this._richlistbox.selectedItems,
+          element => element._shell.isCommandEnabled(aCommand));
     }
   },
 
   _copySelectedDownloadsToClipboard() {
-    let urls = Array.map(this._richlistbox.selectedItems,
-                         element => element._shell.download.source.url);
+    let urls = Array.from(this._richlistbox.selectedItems,
+                          element => element._shell.download.source.url);
 
     Cc["@mozilla.org/widget/clipboardhelper;1"]
       .getService(Ci.nsIClipboardHelper)