refactor: use system level shadow color for elevation

Author: andrewseguin

src/material/core/_m2-app.scss

@@ -19,9 +19,7 @@
   );
 
   @for $zValue from 0 through 24 {
-    $elevation-color: inspection.get-theme-color($theme, foreground, elevation);
-    $shadow: elevation.get-box-shadow($zValue,
-      if($elevation-color == null, elevation.$color, $elevation-color));
+    $shadow: elevation.get-box-shadow($zValue, map.get($system, shadow));
     $tokens: map.set($tokens, 'app-elevation-shadow-level-#{$zValue}', $shadow);
   }
 

src/material/core/m2/_theming.scss

@@ -134,6 +134,7 @@
       hover-state-layer-opacity: 0.04,
       focus-state-layer-opacity: 0.12,
       pressed-state-layer-opacity: 0.12,
+      shadow: black,
     ),
   );
 }
@@ -159,6 +160,7 @@
       hover-state-layer-opacity: 0.04,
       focus-state-layer-opacity: 0.12,
       pressed-state-layer-opacity: 0.12,
+      shadow: black,
     ),
   );
 }

src/material/core/style/_private.scss

@@ -1,18 +1,17 @@
 @use './elevation';
 @use '../theming/inspection';
+@use '../tokens/m2-utils';
+@use '../tokens/m3-utils';
+@use 'sass:map';
 
 @mixin private-theme-elevation($zValue, $theme) {
-  $elevation-color: inspection.get-theme-color($theme, foreground, elevation);
-  $elevation-color-or-default: if($elevation-color == null, elevation.$color, $elevation-color);
-
-  @include elevation.elevation($zValue, $elevation-color-or-default);
+  $system: m2-utils.get-system($theme);
+  @include elevation.elevation($zValue, map.get($system, shadow));
 }
 
 @mixin private-theme-overridable-elevation($zValue, $theme) {
-  $elevation-color: inspection.get-theme-color($theme, foreground, elevation);
-  $elevation-color-or-default: if($elevation-color == null, elevation.$color, $elevation-color);
-
-  @include elevation.overridable-elevation($zValue, $elevation-color-or-default);
+  $system: m2-utils.get-system($theme);
+  @include elevation.overridable-elevation($zValue, map.get($system, shadow));
 }
 
 // If the mat-animation-noop class is present on the components root element,