bug(focus indicators): Added a new _mat-mdc-core mixin with the MDC focus indicator position style.

Author: zelliott

src/dev-app/theme.scss

@@ -15,9 +15,6 @@
 @include angular-material-mdc-typography();
 @include mat-edit-typography(mat-typography-config());
 
-// MDC does not yet have an equivalent to `mat-core` to include this in.
-@include mat-mdc-strong-focus-indicators-base();
-
 // Include base styles for strong focus indicators.
 .demo-strong-focus {
   @include mat-strong-focus-indicators();

src/material-experimental/mdc-helpers/_mdc-helpers.scss

@@ -310,9 +310,9 @@ $mat-typography-level-mappings: (
   }
 }
 
-/// Mixin that applies base styles required for focus indicators to render appropriately.
-/// Should be included once in your app.
-@mixin mat-mdc-strong-focus-indicators-base() {
+// Mixin that applies base styles required for focus indicators to render appropriately.
+// Private mixin included within `_mat-mdc-core`.
+@mixin _mat-mdc-strong-focus-indicators-base() {
   // Ensure that focus indicator host elements are positioned so that the focus indicator
   // pseudo element within is positioned relatively to the host.
   .mat-mdc-focus-indicator {

src/material/core/_core.scss

@@ -15,10 +15,12 @@
 @mixin mat-core($typography-config: null) {
   @include angular-material-typography($typography-config);
   @include mat-ripple();
-  @include mat-strong-focus-indicators-base();
   @include cdk-a11y();
   @include cdk-overlay();
   @include cdk-text-field();
+
+  @include _mat-strong-focus-indicators-base();
+  @include _mat-mdc-core();
 }
 
 // Mixin that renders all of the core styles that depend on the theme.
@@ -55,3 +57,8 @@
     }
   }
 }
+
+// Mixin that renders all of the core MDC styles.
+@mixin _mat-mdc-core() {
+  @include _mat-mdc-strong-focus-indicators-base();
+}

src/material/core/focus-indicators/_focus-indicators.scss

@@ -100,10 +100,10 @@
   }
 }
 
-/// Mixin that applies base styles required for focus indicators to render appropriately.
-/// Automatically included within `mat-core`, should not be directly included in your app.
-@mixin mat-strong-focus-indicators-base() {
-  // Ensure that focus indicator host elements are positioned so that the focus indicator
+// Mixin that applies base styles required for focus indicators to render appropriately.
+// Private mixin included within `mat-core`.
+@mixin _mat-strong-focus-indicators-base() {
+  // Ensures that focus indicator host elements are positioned so that the focus indicator
   // pseudo element within is positioned relatively to the host.
   .mat-focus-indicator {
     position: relative;