fix(select): page scrolling down when selecting option with space (#5192)

Fixes the page being scrolled down if the user presses space to select an option. This is a regression since it used to be handled by the `ListKeyManager`, but it got lost when it was refactored not to disable the default actions.

src/lib/core/option/option.ts

@@ -149,6 +149,9 @@ export class MdOption {
   _handleKeydown(event: KeyboardEvent): void {
     if (event.keyCode === ENTER || event.keyCode === SPACE) {
       this._selectViaInteraction();
+
+      // Prevent the page from scrolling down and form submits.
+      event.preventDefault();
     }
   }
 

src/lib/select/select.spec.ts

@@ -277,6 +277,26 @@ describe('MdSelect', () => {
       expect(panel.classList).toContain('custom-two');
     });
 
+    it('should prevent the default action when pressing SPACE on an option', () => {
+      trigger.click();
+      fixture.detectChanges();
+
+      const option = overlayContainerElement.querySelector('md-option');
+      const event = dispatchKeyboardEvent(option, 'keydown', SPACE);
+
+      expect(event.defaultPrevented).toBe(true);
+    });
+
+    it('should prevent the default action when pressing ENTER on an option', () => {
+      trigger.click();
+      fixture.detectChanges();
+
+      const option = overlayContainerElement.querySelector('md-option');
+      const event = dispatchKeyboardEvent(option, 'keydown', ENTER);
+
+      expect(event.defaultPrevented).toBe(true);
+    });
+
   });
 
   describe('selection logic', () => {