[actionbar] Share button should have a 48px tap target

Share button is an action-icon, and they should have a 48px tap target
per the files-ng spec. Use the same CSS used for {#gear,#sort}-button,
since they are action-icon.

Bug: 1066727
Change-Id: I22ba784fb7357be29a6e62c659f64b008ac588aa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2299559
Commit-Queue: Noel Gordon <noel@chromium.org>
Reviewed-by: Alex Danilo <adanilo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#788540}

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

@@ -788,6 +788,11 @@ body.check-select .dialog-header #search-button > .icon {
 
 .dialog-header.files-ng #share-menu-button > .icon {
   -webkit-mask-image: url(../images/files/ui/share_ng.svg);
+  height: 48px;
+  margin-inline-start: -7px;
+  margin-top: -7px;
+  position: absolute;
+  width: 48px;
 }
 
 body.check-select .dialog-header #share-menu-button > .icon {