[Chromoting] Extract platform checks into platform.js

BUG=

Review URL: https://codereview.chromium.org/618923002

Cr-Commit-Position: refs/heads/master@{#297953}

remoting/remoting_webapp_files.gypi

@@ -59,6 +59,7 @@
       'webapp/base.js',
       'webapp/error.js',
       'webapp/event_handlers.js',
+      'webapp/platform.js',
       'webapp/plugin_settings.js',
       # TODO(garykac) Split out UI client stuff from remoting.js.
       'webapp/remoting.js',

remoting/webapp/platform.js

@@ -0,0 +1,41 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+'use strict';
+
+/** @suppress {duplicate} */
+var remoting = remoting || {};
+
+/**
+ * Returns full Chrome version.
+ * @return {string?}
+ */
+remoting.getChromeVersion = function() {
+  var match = new RegExp('Chrome/([0-9.]*)').exec(navigator.userAgent);
+  if (match && (match.length >= 2)) {
+    return match[1];
+  }
+  return null;
+};
+
+/**
+ * Returns Chrome major version.
+ * @return {number}
+ */
+remoting.getChromeMajorVersion = function() {
+  var match = new RegExp('Chrome/([0-9]+)\.').exec(navigator.userAgent);
+  if (match && (match.length >= 2)) {
+    return parseInt(match[1], 10);
+  }
+  return 0;
+};
+
+/**
+ * Returns whether the app is running on ChromeOS.
+ *
+ * @return {boolean} True if the app is running on ChromeOS.
+ */
+remoting.runningOnChromeOS = function() {
+  return !!navigator.userAgent.match(/\bCrOS\b/);
+}

remoting/webapp/remoting.js

@@ -336,18 +336,6 @@ remoting.getExtensionInfo = function() {
   }
 };
 
-/**
- * Returns Chrome version.
- * @return {string?}
- */
-remoting.getChromeVersion = function() {
-  var match = new RegExp('Chrome/([0-9.]*)').exec(navigator.userAgent);
-  if (match && (match.length >= 2)) {
-    return match[1];
-  }
-  return null;
-};
-
 /**
  * If an IT2Me client or host is active then prompt the user before closing.
  * If a Me2Me client is active then don't bother, since closing the window is
@@ -383,15 +371,6 @@ remoting.signOut = function() {
   document.getElementById('auth-dialog').hidden = false;
 };
 
-/**
- * Returns whether the app is running on ChromeOS.
- *
- * @return {boolean} True if the app is running on ChromeOS.
- */
-remoting.runningOnChromeOS = function() {
-  return !!navigator.userAgent.match(/\bCrOS\b/);
-}
-
 /**
  * Callback function called when the browser window gets a paste operation.
  *