feat(button): Setup elevation overlay

packages/mdc-button/_mixins.scss

@@ -54,6 +54,7 @@ $mdc-button-ripple-target: ".mdc-button__ripple";
   $feat-structure: mdc-feature-create-target($query, structure);
 
   @include mdc-touch-target-wrapper($query);
+  @include mdc-elevation-overlay-common($query);
 
   // postcss-bem-linter: define button
   .mdc-button {
@@ -386,10 +387,12 @@ $query: mdc-feature-all()) {
 
   @include mdc-typography(button, $query);
   @include mdc-button-horizontal-padding($mdc-button-horizontal-padding, $query);
+  @include mdc-elevation-overlay-surface-position($query: $query);
+  @include mdc-elevation-overlay-size(100%, $query: $query);
 
   @include mdc-feature-targets($feat-structure) {
     display: inline-flex;
-    position: relative;
+    // position: relative; already set in mdc-elevation-overlay-surface-position
     align-items: center;
     justify-content: center;
     box-sizing: border-box;

packages/mdc-elevation/README.md

@@ -93,7 +93,7 @@ Mixin | Description
 `mdc-elevation($z-value, $color, $opacity-boost)` | Sets the elevation to the z-space for that given elevation, and optionally sets the color and/or boosts the opacity of the shadow
 `mdc-elevation-overlay-common` | Called once per application to setup the universal elevation overlay styles
 `mdc-elevation-shadow($box-shadow)` | Sets the `box-shadow` of the closest parent selector
-`mdc-elevation-overlay-parent` | Sets the positioning of the overlay's parent element so that the overlay can be appropriately centered
+`mdc-elevation-overlay-surface-position` | Sets the positioning of the overlay's surface element so that the overlay can be appropriately centered
 `mdc-elevation-overlay-size($width, $height: $width)` | Sets the width and height of the elevation overlay
 `mdc-elevation-overlay-fill-color($color)` | Sets the color of the elevation overlay
 `mdc-elevation-overlay-opacity($opacity)` | Sets the opacity of the elevation overlay

packages/mdc-elevation/_mixins.scss

@@ -97,9 +97,9 @@
 }
 
 ///
-/// Sets the elevation overlay parent required positioning.
+/// Sets the elevation overlay surface required positioning.
 ///
-@mixin mdc-elevation-overlay-parent($query: mdc-feature-all()) {
+@mixin mdc-elevation-overlay-surface-position($query: mdc-feature-all()) {
   $feat-structure: mdc-feature-create-target($query, structure);
 
   @include mdc-feature-targets($feat-structure) {