use "platform" as suggested in #360

platform/chromium/vapi-common.js

@@ -0,0 +1,89 @@
+/*******************************************************************************
+
+    µBlock - a Chromium browser extension to block requests.
+    Copyright (C) 2014 The µBlock authors
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see {http://www.gnu.org/licenses/}.
+
+    Home: https://github.com/gorhill/uBlock
+*/
+
+// For background page or non-background pages
+
+/* global self, vAPI */
+
+/******************************************************************************/
+
+(function() {
+
+'use strict';
+
+self.vAPI = self.vAPI || {};
+
+/******************************************************************************/
+
+// http://www.w3.org/International/questions/qa-scripts#directions
+
+var setScriptDirection = function(language) {
+    document.body.setAttribute(
+        'dir',
+        ['ar', 'he', 'fa', 'ps', 'ur'].indexOf(language) !== -1 ? 'rtl' : 'ltr'
+    );
+};
+
+/******************************************************************************/
+
+vAPI.download = function(details) {
+    if ( !details.url ) {
+        return;
+    }
+
+    var a = document.createElement('a');
+
+    if ( 'download' in a ) {
+        a.href = details.url;
+        a.setAttribute('download', details.filename || '');
+        a.dispatchEvent(new MouseEvent('click'));
+        return;
+    }
+    var messager = vAPI.messaging.channel('_download');
+    messager.send({
+        what: 'gotoURL',
+        details: {
+            url: details.url,
+            index: -1
+        }
+    });
+    messager.close();
+};
+
+/******************************************************************************/
+
+var chrome = self.chrome;
+
+vAPI.getURL = function(path) {
+    return chrome.runtime.getURL(path);
+};
+
+vAPI.i18n = function(s) {
+    return chrome.i18n.getMessage(s);
+};
+
+setScriptDirection(vAPI.i18n('@@ui_locale'));
+
+/******************************************************************************/
+
+})();
+
+/******************************************************************************/