Move the overlay coloring to the button theme.

Author: crisbeto

src/lib/button/_button-theme.scss

@@ -80,6 +80,12 @@
     background-color: md-color($accent);
     color: md-color($accent, default-contrast);
   }
+
+  .md-button-focus-overlay {
+    @include md-high-contrast {
+      background-color: if(map_get($theme, is-dark), rgba(black, 0.5), rgba(white, 0.5));
+    }
+  }
 }
 
 

src/lib/button/button.scss

@@ -80,10 +80,6 @@
   border-radius: inherit;
   pointer-events: none;
   opacity: 0;
-
-  @include md-high-contrast {
-    background-color: rgba(white, 0.5);
-  }
 }
 
 // For round buttons, the ripple container should clip child ripples to a circle.