Files app: Hide list/grid scrollbar when splitter resize is active

When the user is resizing the app using the splitter, and the tree has
has overflow-y content, a scroll bar appears. That is annoying. Fix by
hiding directory scroll bars while the splitter is active.

Similar to what was done for directory tree on CL:1851789

Bug: 992821
Change-Id: Ic11d88a943af4a756496e6f18b78910249c87be0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1858026
Auto-Submit: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Commit-Queue: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#705480}

ui/file_manager/file_manager/foreground/css/list.css

@@ -44,6 +44,11 @@ grid > [selected] {
   z-index: 2;
 }
 
+html[class*='col-resize'] list,
+html[class*='col-resize'] grid {
+  overflow-y: hidden !important;
+}
+
 list > .spacer,
 grid > .spacer {
   box-sizing: border-box;