Reland "Datagrid A11y: Select datagrid row on up/down arrow key press"

This is a reland of 1c2fd924f064d2f19785c6c4c22d755e8b26daf0

This change is missing from master for some reason. Relanding

Original change's description:
> Datagrid A11y: Select datagrid row on up/down arrow key press
>
> This CL adds the ability to select the first or last entry in
> a datagrid when it receives focus by pressing the up or down arrow
> key. This change is to allow keyboard users to access the datagrid
> without using a mouse.
>
> Before: https://imgur.com/EkqXd95
>
> After: https://imgur.com/fO3qp9W
>
> Bug: 963183
>
>
> Change-Id: I7b5ee2f2b5ff535bca9a2a10f5efe177c1322668
> Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/1881219
> Reviewed-by: Lorne Mitchell <[email protected]>
> Reviewed-by: Jan Scheffler <[email protected]>
> Commit-Queue: Brandon Goddard <[email protected]>

Bug: 963183
Change-Id: Ic9bda6a202039374a865e9a8109b679c6430a640
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/1895993
Reviewed-by: Lorne Mitchell <[email protected]>
Commit-Queue: Brandon Goddard <[email protected]>
diff --git a/front_end/network/networkLogView.css b/front_end/network/networkLogView.css
index 51ca477..7609193 100644
--- a/front_end/network/networkLogView.css
+++ b/front_end/network/networkLogView.css
@@ -29,7 +29,7 @@
  */
 
 .network-log-grid.data-grid {
-    border: none;
+    border: none !important;
     flex: auto;
 }