fix(dialog): backdrop not being removed if it doesn't have transitions

Fixes the dialog's backdrop not being removed if it's transition have been disabled.

Fixes #1607.

src/lib/core/overlay/overlay-ref.ts

@@ -92,7 +92,9 @@ export class OverlayRef implements PortalHost {
 
     // Add class to fade-in the backdrop after one frame.
     requestAnimationFrame(() => {
-      this._backdropElement.classList.add('md-overlay-backdrop-showing');
+      if (this._backdropElement) {
+        this._backdropElement.classList.add('md-overlay-backdrop-showing');
+      }
     });
   }
 
@@ -101,18 +103,28 @@ export class OverlayRef implements PortalHost {
     let backdropToDetach = this._backdropElement;
 
     if (backdropToDetach) {
-      backdropToDetach.classList.remove('md-overlay-backdrop-showing');
-      backdropToDetach.classList.remove(this._state.backdropClass);
-      backdropToDetach.addEventListener('transitionend', () => {
-        backdropToDetach.parentNode.removeChild(backdropToDetach);
+      let onTransitionEnd = () => {
+        // It may not be attached to anything in certain cases (e.g. unit tests).
+        if (backdropToDetach && backdropToDetach.parentNode) {
+          backdropToDetach.parentNode.removeChild(backdropToDetach);
+        }
 
         // It is possible that a new portal has been attached to this overlay since we started
         // removing the backdrop. If that is the case, only clear the backdrop reference if it
         // is still the same instance that we started to remove.
         if (this._backdropElement == backdropToDetach) {
           this._backdropElement = null;
         }
-      });
+      };
+
+      backdropToDetach.classList.remove('md-overlay-backdrop-showing');
+      backdropToDetach.classList.remove(this._state.backdropClass);
+      backdropToDetach.addEventListener('transitionend', onTransitionEnd);
+
+      // If the backdrop doesn't have a transition, the `transitionend` event won't fire.
+      // In this case we make it unclickable and we try to remove it after a delay.
+      backdropToDetach.style.pointerEvents = 'none';
+      setTimeout(onTransitionEnd, 500);
     }
   }
 }

src/lib/dialog/dialog.spec.ts

@@ -5,6 +5,7 @@ import {
   flushMicrotasks,
   ComponentFixture,
   TestBed,
+  tick,
 } from '@angular/core/testing';
 import {By} from '@angular/platform-browser';
 import {NgModule, Component, Directive, ViewChild, ViewContainerRef} from '@angular/core';
@@ -207,6 +208,7 @@ describe('MdDialog', () => {
           .not.toBe('dialog-trigger', 'Expected the focus to change when dialog was opened.');
 
       dialogRef.close();
+      tick(500);
       viewContainerFixture.detectChanges();
       flushMicrotasks();