Apply the dialog ok button color with hover as well as without.

Currently, the hover color for dialog ok buttons is not set, so it falls
through to the default button color, which varies depending on whether
check-select is applied to the body. This causes hovering to make the
text color dark instead of remaining unchanged. Set the color for both
with and without hover to avoid this.

Bug: 842130
Change-Id: I67a02346a7aa173de91ac41366cbdd5057e9e6c3
Reviewed-on: https://chromium-review.googlesource.com/c/1345169
Commit-Queue: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609832}

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

@@ -143,7 +143,8 @@ cr-menu.chrome-menu > [checked]::before {
   padding: auto;
 }
 
-.cr-dialog-buttons > button.cr-dialog-ok {
+.cr-dialog-buttons > button.cr-dialog-ok,
+.cr-dialog-buttons > button.cr-dialog-ok:hover {
   background-color: rgb(51, 103, 214);
   color: white;
   order: 1;