Files.app: fix a bug that low-space warning is not shown at all.

fileBrowserPrivate.getSizeStats takes volumeId as the argument,
not the root URL.

BUG=350101

Review URL: https://codereview.chromium.org/218623020

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@261444 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/resources/file_manager/foreground/js/drive_banners.js

@@ -521,7 +521,7 @@ FileListBannerController.prototype.maybeShowLowSpaceWarning_ = function(
     return;
 
   chrome.fileBrowserPrivate.getSizeStats(
-      volume.fileSystem.root.toURL(),
+      volume.volumeId,
       function(sizeStats) {
         var currentVolume = this.volumeManager_.getVolumeInfo(
             this.directoryModel_.getCurrentDirEntry());