Fix washed out text in Breadcrumbs overflow button
Fix washed out text in Breadcrumbs overflow button

This CL fixes two problems:

1. An old CSS declaration was accidentally left in and prevented us
   using the new theme colors.
2. A disabled overflow button looked visually identical to an enabled
   button, so I added some CSS to make disabled buttons 50% opacity as a
   visual cue they are not enabled.

Fixed: 1153276
Change-Id: Ic67b8d579549f8c64080ab51993fd6cb8f6da635
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2573367
Commit-Queue: Jack Franklin <993fcadce4d04090da2fefd557a0995e7966c8d5@chromium.org>
Auto-Submit: Jack Franklin <993fcadce4d04090da2fefd557a0995e7966c8d5@chromium.org>
Reviewed-by: Tim van der Lippe <dba8716ee7f8d16236046f74d2167cb94410f6ed@chromium.org>

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