Restore scrolling in BackForwardCacheView when contents overflow

Fix an issue with large cache test report contents not being viewable
if they do not fit in available area. Restore vertical scroll to let
user see the whole report.

Fixed: 483648154
Change-Id: Icbef851eb6730c7e317bab6ba80223c1e3176439
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/7734966
Commit-Queue: Wolfgang Beyer <wolfi@chromium.org>
Reviewed-by: Wolfgang Beyer <wolfi@chromium.org>
Commit-Queue: Piotr Paulski <piotrpaulski@chromium.org>
Auto-Submit: Piotr Paulski <piotrpaulski@chromium.org>

Author: Piotr Paulski

front_end/panels/application/components/backForwardCacheView.css

@@ -4,6 +4,10 @@
  * found in the LICENSE file.
  */
 
+:host {
+  overflow: auto;
+}
+
 devtools-report-value {
   overflow: hidden;
 }