feat(dialog): add enter/exit animations

* Adds enter/exit animations to the dialog.
* Refactors the `MdDialogContainer` and `MdDialogRef` to accommodate the animations.
* Fixes some test failures due to the animations.
* Allows for the backdrop to be detached before the rest of the overlay, in order to allow for it to be transitioned in parallel.

Fixes angular#2665.

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

@@ -47,7 +47,7 @@ export class OverlayRef implements PortalHost {
    * @returns Resolves when the overlay has been detached.
    */
   detach(): Promise<any> {
-    this._detachBackdrop();
+    this.detachBackdrop();
     return this._portalHost.detach();
   }
 
@@ -59,7 +59,7 @@ export class OverlayRef implements PortalHost {
       this._state.positionStrategy.dispose();
     }
 
-    this._detachBackdrop();
+    this.detachBackdrop();
     this._portalHost.dispose();
   }
 
@@ -138,7 +138,7 @@ export class OverlayRef implements PortalHost {
   }
 
   /** Detaches the backdrop (if any) associated with the overlay. */
-  private _detachBackdrop(): void {
+  detachBackdrop(): void {
     let backdropToDetach = this._backdropElement;
 
     if (backdropToDetach) {

src/lib/dialog/dialog-container.ts

@@ -5,30 +5,51 @@ import {
   ViewEncapsulation,
   NgZone,
   OnDestroy,
+  animate,
+  state,
+  style,
+  transition,
+  trigger,
+  AnimationTransitionEvent,
+  EventEmitter,
 } from '@angular/core';
 import {BasePortalHost, ComponentPortal, PortalHostDirective, TemplatePortal} from '../core';
 import {MdDialogConfig} from './dialog-config';
-import {MdDialogRef} from './dialog-ref';
 import {MdDialogContentAlreadyAttachedError} from './dialog-errors';
 import {FocusTrap} from '../core/a11y/focus-trap';
 import 'rxjs/add/operator/first';
 
 
+/** Possible states for the dialog container animation. */
+export type MdDialogContainerAnimationState = 'void' | 'enter' | 'exit' | 'exit-start';
+
+
 /**
  * Internal component that wraps user-provided dialog content.
+ * Animation is based on https://material.io/guidelines/motion/choreography.html.
  * @docs-private
  */
 @Component({
   moduleId: module.id,
   selector: 'md-dialog-container, mat-dialog-container',
   templateUrl: 'dialog-container.html',
   styleUrls: ['dialog.css'],
+  encapsulation: ViewEncapsulation.None,
+  animations: [
+    trigger('slideDialog', [
+      state('void', style({ transform: 'translateY(25%) scale(0.9)', opacity: 0 })),
+      state('enter', style({ transform: 'translateY(0%) scale(1)', opacity: 1 })),
+      state('exit', style({ transform: 'translateY(25%)', opacity: 0 })),
+      transition('* => *', animate('400ms cubic-bezier(0.25, 0.8, 0.25, 1)')),
+    ])
+  ],
   host: {
     'class': 'md-dialog-container',
     '[attr.role]': 'dialogConfig?.role',
-    '(keydown.escape)': 'handleEscapeKey()',
+    '(keydown.escape)': '_handleEscapeKey()',
+    '[@slideDialog]': '_state',
+    '(@slideDialog.done)': '_onAnimationDone($event)',
   },
-  encapsulation: ViewEncapsulation.None,
 })
 export class MdDialogContainer extends BasePortalHost implements OnDestroy {
   /** The portal host inside of this container into which the dialog content will be loaded. */
@@ -43,8 +64,11 @@ export class MdDialogContainer extends BasePortalHost implements OnDestroy {
   /** The dialog configuration. */
   dialogConfig: MdDialogConfig;
 
-  /** Reference to the open dialog. */
-  dialogRef: MdDialogRef<any>;
+  /** State of the dialog animation. */
+  _state: MdDialogContainerAnimationState = 'enter';
+
+  /** Emits the current animation state whenever it changes. */
+  _onAnimationStateChange = new EventEmitter<MdDialogContainerAnimationState>();
 
   constructor(private _ngZone: NgZone) {
     super();
@@ -77,22 +101,40 @@ export class MdDialogContainer extends BasePortalHost implements OnDestroy {
     throw Error('Not yet implemented');
   }
 
+  ngOnDestroy() {
+    // When the dialog is destroyed, return focus to the element that originally had it before
+    // the dialog was opened. Wait for the DOM to finish settling before changing the focus so
+    // that it doesn't end up back on the <body>.
+    this._ngZone.onMicrotaskEmpty.first().subscribe(() => {
+      (this._elementFocusedBeforeDialogWasOpened as HTMLElement).focus();
+      this._onAnimationStateChange.complete();
+    });
+  }
+
   /**
    * Handles the user pressing the Escape key.
    * @docs-private
    */
-  handleEscapeKey() {
+  _handleEscapeKey() {
     if (!this.dialogConfig.disableClose) {
-      this.dialogRef.close();
+      this._exit();
     }
   }
 
-  ngOnDestroy() {
-    // When the dialog is destroyed, return focus to the element that originally had it before
-    // the dialog was opened. Wait for the DOM to finish settling before changing the focus so
-    // that it doesn't end up back on the <body>.
-    this._ngZone.onMicrotaskEmpty.first().subscribe(() => {
-      (this._elementFocusedBeforeDialogWasOpened as HTMLElement).focus();
-    });
+  /**
+   * Kicks off the leave animation.
+   * @docs-private
+   */
+  _exit(): void {
+    this._state = 'exit';
+    this._onAnimationStateChange.emit('exit-start');
+  }
+
+  /**
+   * Callback, invoked whenever an animation on the host completes.
+   * @docs-private
+   */
+  _onAnimationDone(event: AnimationTransitionEvent) {
+    this._onAnimationStateChange.emit(event.toState as MdDialogContainerAnimationState);
   }
 }

src/lib/dialog/dialog-ref.ts

@@ -1,6 +1,7 @@
 import {OverlayRef} from '../core';
 import {Observable} from 'rxjs/Observable';
 import {Subject} from 'rxjs/Subject';
+import {MdDialogContainer, MdDialogContainerAnimationState} from './dialog-container';
 
 
 // TODO(jelbourn): resizing
@@ -17,16 +18,30 @@ export class MdDialogRef<T> {
   /** Subject for notifying the user that the dialog has finished closing. */
   private _afterClosed: Subject<any> = new Subject();
 
-  constructor(private _overlayRef: OverlayRef) { }
+  /** Result to be passed to afterClosed. */
+  private _result: any;
+
+  constructor(private _overlayRef: OverlayRef, private _containerInstance: MdDialogContainer) {
+    _containerInstance._onAnimationStateChange.subscribe(
+      (state: MdDialogContainerAnimationState) => {
+        if (state === 'exit-start') {
+          // Transition the backdrop in parallel with the dialog.
+          this._overlayRef.detachBackdrop();
+        } else if (state === 'exit') {
+          this._overlayRef.dispose();
+          this._afterClosed.next(this._result);
+          this._afterClosed.complete();
+        }
+      });
+  }
 
   /**
    * Close the dialog.
    * @param dialogResult Optional result to return to the dialog opener.
    */
   close(dialogResult?: any): void {
-    this._overlayRef.dispose();
-    this._afterClosed.next(dialogResult);
-    this._afterClosed.complete();
+    this._result = dialogResult;
+    this._containerInstance._exit();
   }
 
   /**