Change start padding of input and dropdown elements in cr-searchable-dropdown

This causes the input and dropdown text elements to be aligned together.

BUG=977313

Change-Id: I5eca12ab5a5f2b600a1e419309f68d0c1ccc6bff
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1819093
Commit-Queue: Anand Mistry <amistry@chromium.org>
Reviewed-by: Michael Giuffrida <michaelpg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#699636}

ui/webui/resources/cr_elements/cr_searchable_drop_down/cr_searchable_drop_down.html

@@ -21,6 +21,10 @@
         width: var(--cr-searchable-drop-down-width, 472px);
       }
 
+      cr-input {
+        --cr-input-padding-start: 8px;
+      }
+
       iron-dropdown {
         max-height: 270px;
       }
@@ -90,7 +94,7 @@
         color: var(--paper-grey-900);
         font: inherit;
         min-height: 32px;
-        padding: 0 24px;
+        padding: 0 8px;
         text-align: start;
         width: 100%;
       }