test: update theming index sass test to test density and use correct API

Also ensures these tests run with `--only_build_tests`, ensuring they
run in the MDC snapshot test job.

Author: devversion

src/material/core/theming/tests/BUILD.bazel

@@ -1,4 +1,5 @@
 load("//tools:defaults.bzl", "jasmine_node_test", "sass_binary", "ts_library")
+load("@bazel_skylib//rules:build_test.bzl", "build_test")
 
 package(default_visibility = ["//visibility:public"])
 
@@ -44,6 +45,16 @@ sass_binary(
     deps = ["//src/material:sass_lib"],
 )
 
+build_test(
+    name = "sass_compile_tetss",
+    targets = [
+        ":test-css-variables-theme",
+        ":test-theming-api",
+        ":test-theming-bundle",
+        ":test-legacy-theming-bundle",
+    ],
+)
+
 ts_library(
     name = "unit_test_lib",
     testonly = True,

src/material/core/theming/tests/test-theming-bundle.scss

@@ -11,8 +11,8 @@ mat.$theme-ignore-duplication-warnings: true;
 
 $theme: mat.define-light-theme((
   color: (
-    primary: mat.$red-palette,
-    accent: mat.$blue-palette,
+    primary: mat.define-palette(mat.$red-palette),
+    accent: mat.define-palette(mat.$blue-palette),
   ),
   density: -2,
 ));
@@ -22,10 +22,23 @@ $theme: mat.define-light-theme((
 @include mat.all-component-themes($theme);
 @include mat.all-component-typographies();
 @include mat.all-component-colors($theme);
-@include mat.all-legacy-component-themes($theme);
-@include mat.all-legacy-component-typographies();
-@include mat.all-legacy-component-colors($theme);
+
+@include mat.private-all-component-densities($theme);
+@include mat.private-all-component-densities((density: 0));
+@include mat.private-all-component-densities((density: -1));
+@include mat.private-all-component-densities((density: minimum));
+
 @include mat.core-theme($theme);
 @include mat.button-theme($theme);
+
 @include mat.strong-focus-indicators();
 @include mat.strong-focus-indicators-theme($theme);
+
+// Legacy.
+@include mat.all-legacy-component-themes($theme);
+@include mat.all-legacy-component-typographies();
+@include mat.all-legacy-component-colors($theme);
+@include mat.private-all-legacy-component-densities($theme);
+@include mat.private-all-legacy-component-densities((density: 0));
+@include mat.private-all-legacy-component-densities((density: -1));
+@include mat.private-all-legacy-component-densities((density: minimum));