DevTools: Text-boxes border are not seen properly on ‘Add box-shadow' dialog.

Bug: 831087
Change-Id: Ife9e0fde092818be3c08c4e7fde2cd55bcfd4cef
TBR: dgozman
Reviewed-on: https://chromium-review.googlesource.com/1005360Reviewed-by: Pavel Feldman <pfeldman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550322}

third_party/blink/renderer/devtools/front_end/inline_editor/cssShadowEditor.css

@@ -88,4 +88,5 @@
     width: 52px;
     margin-right: 8px;
     text-align: right;
+    box-shadow: var(--focus-ring-inactive-shadow);
 }