Apply theme to 5.3.8

scss/_reboot.scss

@@ -87,7 +87,7 @@ hr {
   font-style: $headings-font-style;
   font-weight: $headings-font-weight;
   line-height: $headings-line-height;
-  color: $headings-color;
+  color: var(--#{$prefix}heading-color);
 }
 
 h1 {
@@ -217,6 +217,7 @@ small {
 
 mark {
   padding: $mark-padding;
+  color: var(--#{$prefix}highlight-color);
   background-color: var(--#{$prefix}highlight-bg);
 }
 
@@ -241,11 +242,11 @@ sup { top: -.5em; }
 // Links
 
 a {
-  color: var(--#{$prefix}link-color);
+  color: rgba(var(--#{$prefix}link-color-rgb), var(--#{$prefix}link-opacity, 1));
   text-decoration: $link-decoration;
 
   &:hover {
-    color: var(--#{$prefix}link-hover-color);
+    --#{$prefix}link-color-rgb: var(--#{$prefix}link-hover-color-rgb);
     text-decoration: $link-hover-decoration;
   }
 }
@@ -498,9 +499,9 @@ legend {
   width: 100%;
   padding: 0;
   margin-bottom: $legend-margin-bottom;
-  @include font-size($legend-font-size);
   font-weight: $legend-font-weight;
   line-height: inherit;
+  @include font-size($legend-font-size);
 
   + * {
     clear: left; // 2
@@ -524,15 +525,21 @@ legend {
   height: auto;
 }
 
-// 1. Correct the outline style in Safari.
-// 2. This overrides the extra rounded corners on search inputs in iOS so that our
+// 1. This overrides the extra rounded corners on search inputs in iOS so that our
 //    `.form-control` class can properly style them. Note that this cannot simply
 //    be added to `.form-control` as it's not specific enough. For details, see
 //    https://github.com/twbs/bootstrap/issues/11586.
+// 2. Correct the outline style in Safari.
 
 [type="search"] {
-  outline-offset: -2px; // 1
-  -webkit-appearance: textfield; // 2
+  -webkit-appearance: textfield; // 1
+  outline-offset: -2px; // 2
+
+  // 3. Better affordance and consistent appearance for search cancel button
+  &::-webkit-search-cancel-button {
+    cursor: pointer;
+    filter: grayscale(1);
+  }
 }
 
 // 1. A few input types should stay LTR