Support compilation extrafiles on ChromeOS

Similarly to what has been done in #498, we're adding support to extrafiles compilation on ChromeOS as well.

See also #498

Author: csarnataro

package.json

@@ -1,6 +1,6 @@
 {
   "name": "arduino-create-agent-js-client",
-  "version": "2.6.0",
+  "version": "2.7.0",
   "description": "JS module providing discovery of the Arduino Create Plugin and communication with it",
   "main": "lib/index.js",
   "module": "es/index.js",

src/chrome-app-daemon.js

@@ -239,7 +239,8 @@ export default class ChromeOsDaemon extends Daemon {
    */
   _upload(uploadPayload, uploadCommandInfo) {
     const { board, port, commandline, data } = uploadPayload;
-      try {
+    const extrafiles = uploadCommandInfo && uploadCommandInfo.files && Array.isArray(uploadCommandInfo.files) || []
+    try {
       window.oauth.token().then(token => {
         this.channel.postMessage({
           command: 'upload',
@@ -249,7 +250,7 @@ export default class ChromeOsDaemon extends Daemon {
             commandline,
             data,
             token: token.token,
-            extrafiles: uploadCommandInfo.files || []
+            extrafiles
           }
         });
       });