Hide the automatically displayed webkit-only clear/cancel search button. (#8538)

Author: isoos

pkg/web_css/lib/src/_search.scss

@@ -47,6 +47,12 @@
     &:focus {
       outline: none;
     }
+
+    // This is a non-standard feature, supported only by webkit browsers
+    // https://developer.mozilla.org/en-US/docs/Web/CSS/::-webkit-search-cancel-button
+    &::-webkit-search-cancel-button {
+      display: none;
+    }
   }
 
   >.icon {

pkg/web_css/test/expression_test.dart

@@ -42,6 +42,7 @@ void main() {
         'keyframes',
         'last-child',
         'nth-child',
+        '-webkit-search-cancel-button',
       ]);
       // composite patterns
       expressions.removeWhere((e) => e.startsWith('home-block-'));