fix(button): focus styles not applied to programmatically focused buttons

Currently the tint that is added on top of focused buttons won't show up if the button is focused programmatically, which means that the button won't appear focused in cases like the dialog closing and restoring focus to its trigger. This seems to have been introduced by 5d6920d.

Author: crisbeto

src/demo-app/button/button-demo.html

@@ -73,11 +73,12 @@
       <button md-raised-button (click)="button1.focus()">Focus 1</button>
       <button md-raised-button (click)="button2.focus()">Focus 2</button>
       <button md-raised-button (click)="button3.focus()">Focus 3</button>
+      <button md-raised-button (click)="button4.focus()">Focus 4</button>
     </div>
     <button md-button #button1 [disabled]="isDisabled" (click)="clickCounter=clickCounter+1">off</button>
-    <button md-button color="primary" [disabled]="isDisabled">off</button>
-    <a href="http://www.google.com" #button2 md-button color="accent" [disabled]="isDisabled">off</a>
-    <button md-raised-button #button3 color="primary" [disabled]="isDisabled">off</button>
+    <button md-button color="primary" #button2 [disabled]="isDisabled">off</button>
+    <a href="http://www.google.com" #button3 md-button color="accent" [disabled]="isDisabled">off</a>
+    <button md-raised-button #button4 color="primary" [disabled]="isDisabled">off</button>
     <button md-mini-fab [disabled]="isDisabled">
       <md-icon class="md-24">check</md-icon>
     </button>

src/lib/button/_button-base.scss

@@ -51,7 +51,7 @@ $mat-mini-fab-padding: 8px !default;
     cursor: default;
   }
 
-  &.cdk-keyboard-focused {
+  &.cdk-keyboard-focused, &.cdk-program-focused {
     .mat-button-focus-overlay {
       opacity: 1;
     }