[NaCl SDK] Add filesystem passing example.

native_client_sdk/src/examples/tutorial/filesystem_passing/example.js

+// Copyright (c) 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.
+
+function attachListeners() {
+  document.getElementById('choosedir').addEventListener('click', function(e) {
+    chrome.fileSystem.chooseEntry({type: 'openDirectory'}, function(entry) {
+      if (!entry) {
+        // The user cancelled the dialog.
+        return;
+      }
+
+      // Send the filesystem and the directory path to the NaCl module.
+      common.naclModule.postMessage({
+        filesystem: entry.filesystem,
+        fullPath: entry.fullPath
+      });
+    });
+  }, false);
+}
+
+// Called by the common.js module.
+function moduleDidLoad() {
+  // The module is not hidden by default so we can easily see if the plugin
+  // failed to load.
+  common.hideModule();
+
+  // Make sure this example is running as an App. If not, display a warning.
+  if (!chrome.fileSystem) {
+    common.updateStatus('Error: must be run as an App.');
+    return;
+  }
+}
+
+// Called by the common.js module.
+function handleMessage(message_event) {
+  common.logMessage(message_event.data);
+}