Introduce a file-manager-new-ui flag for the new UI of Files.app.

chrome/browser/resources/file_manager/js/util.js

Index: chrome/browser/resources/file_manager/js/util.js
diff --git a/chrome/browser/resources/file_manager/js/util.js b/chrome/browser/resources/file_manager/js/util.js
index c628a2e31bf2ab3387f46ad718daaef18c20c172..650be715ec9a4cd1ffdaa250fdaabf71ecb49bcb 100644
--- a/chrome/browser/resources/file_manager/js/util.js
+++ b/chrome/browser/resources/file_manager/js/util.js
@@ -815,6 +815,16 @@ util.platform = {
   },
 
   /**
+   * @return {boolean} True for the new ui.
+   */
+  newUI: function() {
+    if (!util.platform.v2())
+      return false;
+    var manifest = chrome.runtime.getManifest();
+    return manifest.version >= 3.0;
+  },
+
+  /**
    * @param {function(Object)} callback Function accepting a preference map.
    */
   getPreferences: function(callback) {