refactor(material/button): switch flat-button to density tokens

Author: wagnermaciel

src/material/button/_button-theme.scss

@@ -207,9 +207,13 @@
 @mixin density($theme) {
   $density-scale: theming.clamp-density(inspection.get-theme-density($theme), -3);
 
+  .mat-mdc-unelevated-button {
+    $density-tokens: tokens-mdc-button-filled.get-density-tokens($theme);
+    @include mdc-button-filled-theme.theme($density-tokens);
+  }
+
   .mat-mdc-button,
   .mat-mdc-raised-button,
-  .mat-mdc-unelevated-button,
   .mat-mdc-outlined-button {
     // Use `mat-mdc-button-base` to increase the specificity over the button's structural styles.
     &.mat-mdc-button-base {

src/material/core/tokens/m2/mdc/_button-filled.scss

@@ -1,7 +1,9 @@
+@use 'sass:map';
 @use '../../token-utils';
 @use '../../../mdc-helpers/mdc-helpers';
 @use '../../../style/sass-utils';
 @use '../../../theming/inspection';
+@use '../../../theming/theming';
 
 // The prefix used to generate the fully qualified name for tokens in this file.
 $prefix: (mdc, button-filled);
@@ -15,8 +17,6 @@ $prefix: (mdc, button-filled);
 @function get-unthemable-tokens() {
   @return (
     container-elevation: 0,
-    container-height: 36px,
-    container-shape: 4px,
     disabled-container-elevation: 0,
     focus-container-elevation: 0,
     hover-container-elevation: 0,
@@ -77,7 +77,21 @@ $prefix: (mdc, button-filled);
 
 // Tokens that can be configured through Angular Material's density theming API.
 @function get-density-tokens($theme) {
-  @return ();
+  $scale: theming.clamp-density(inspection.get-theme-density($theme), -3);
+
+  @return (
+    container-height:
+      map.get(
+        (
+          0: 36px,
+          -1: 32px,
+          -2: 28px,
+          -3: 24px,
+        ),
+        $scale
+      ),
+    container-shape: 4px
+  );
 }
 
 // Combines the tokens generated by the above functions into a single map with placeholder values.