Keep Drive expanded when My files is disabled

Change NavigationListModel to expose the flag state and use it from
DriveVolumeItem to only expand if My files is disabled.

Fix comment comment changed in crrev.com/c/1141454.

browser tests check for collapsed behaviour.

Test: Manually checked that Drive is expanded when flag is disabled,
Bug: 864291
Cq-Include-Trybots: luci.chromium.try:closure_compilation
Change-Id: Iff2c364ce5ad8d50dfd8f7850d9773c8ddf47b3d
Reviewed-on: https://chromium-review.googlesource.com/1143044Reviewed-by: Noel Gordon <noel@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576399}

ui/file_manager/file_manager/foreground/js/navigation_list_model.js

@@ -428,6 +428,10 @@ NavigationListModel.prototype = {
     this.linuxFilesItem_ = item;
     this.reorderNavigationItems_();
   },
+  /** @type {boolean} */
+  get disableMyFilesNavigation() {
+    return this.disableMyFilesNavigation_;
+  }
 };
 
 /**

ui/file_manager/file_manager/foreground/js/ui/directory_tree.js

@@ -1049,6 +1049,10 @@ DriveVolumeItem.prototype.updateSubDirectories = function(recursive) {
     this.add(item);
     item.updateSubDirectories(false);
   }
+  // When My files is disabled Drive should be expanded by default.
+  // TODO(crbug.com/850348): Remove this once flag is removed.
+  if (this.parentTree_.dataModel.disableMyFilesNavigation)
+    this.expanded = true;
 };
 
 /**
@@ -1628,8 +1632,8 @@ DirectoryTree.prototype.updateSubElementsFromList = function(recursive) {
       if (recursive && currentItem instanceof VolumeItem)
         currentItem.updateSubDirectories(true);
       // EntryListItem can contain volumes that might have been updated: ask
-      // them to re-draw. It only needs to update the first level of children,
-      // so it doesn't need to be recursive.
+      // them to re-draw. Updates recursively so any created or removed children
+      // folder can be reflected on directory tree.
       if (currentItem instanceof EntryListItem)
         currentItem.updateSubDirectories(true);
     } else {