Respect opt_scopes in getNewToken.

Without this, the downscoped token was being revoked, but the call to get a
fresh one was returning the cached non-downscoped token.

Also adds an assert to catch regressions.

BUG=b/20662147

Review URL: https://codereview.chromium.org/1123183005

Cr-Commit-Position: refs/heads/master@{#329711}

remoting/webapp/app_remoting/js/app_connected_view.js

@@ -239,10 +239,16 @@ remoting.AppConnectedView.prototype.sendGoogleDriveAccessToken_ =
   ];
   remoting.identity.getNewToken(googleDriveScopes).then(
     function(/** string */ token){
+      base.debug.assert(token !== previousToken_);
+      previousToken_ = token;
       sendExtensionMessage('accessToken', token);
   }).catch(remoting.Error.handler(function(/** remoting.Error */ error) {
     console.log('Failed to refresh access token: ' + error.toString());
   }));
 };
 
+// The access token last received from getNewToken. Saved to ensure that we
+// get a fresh token each time.
+var previousToken_ = '';
+
 })();

remoting/webapp/base/js/identity.js

@@ -95,7 +95,7 @@ remoting.Identity.prototype.getNewToken = function(opt_scopes) {
   return this.getToken(opt_scopes).then(function(/** string */ token) {
     return new Promise(function(resolve, reject) {
       chrome.identity.removeCachedAuthToken({'token': token }, function() {
-        resolve(that.getToken());
+        resolve(that.getToken(opt_scopes));
       });
     });
   });