Disallow dragging app list folder to the taskbar for the Windows app list.

This CL prevents the dragging of app list folders to the Windows taskbar
by disabling synchronous drags for folders.

BUG=371665

Review URL: https://codereview.chromium.org/279673002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@269515 0039d316-1c4b-4281-b951-d872f2087c98

ui/app_list/views/apps_grid_view.cc

@@ -477,6 +477,10 @@ void AppsGridView::StartSettingUpSynchronousDrag() {
   if (!delegate_)
     return;
 
+  // Folders can't be integrated with the OS.
+  if (IsFolderItem(drag_view_->item()))
+    return;
+
   // Favor the drag and drop host over native win32 drag. For the Win8/ash
   // launcher we want to have ashes drag and drop over win32's.
   if (drag_and_drop_host_)