[selectionbar] Enable hover color for files-ng

Changes the setting of 'transparent' background color to only apply for
the non files-ng case - allowing the files-ng background color to
inherit.

This also has the side-effect of allowing all the files-ng background
color rules to work as well (e.g. no hover color when pointer is active).

Bug: 1068079
Change-Id: Icb4611d9138404b8ba9854e518619adf02c44246
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2138936Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: Alex Danilo <adanilo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#756974}

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

@@ -1035,7 +1035,6 @@ body.check-select #files-selected-label {
 
 #cancel-selection-button {
   --ink-color: currentColor;
-  background-color: transparent;
   border: none;
   box-shadow: none;
   color: currentColor;
@@ -1043,6 +1042,10 @@ body.check-select #files-selected-label {
   text-transform: none;
 }
 
+body:not(.files-ng) #cancel-selection-button {
+  background-color: transparent;
+}
+
 /* TODO(adanilo) document the calc() reason. */
 body.files-ng #cancel-selection-button {
   border: 1px solid transparent;