fix(select): fix initial values with reactive forms

Closes #1973

Author: kara

src/demo-app/select/select-demo.ts

@@ -11,7 +11,7 @@ export class SelectDemo {
   isRequired = false;
   isDisabled = false;
   currentDrink: string;
-  foodControl = new FormControl('');
+  foodControl = new FormControl('pizza-1');
 
   foods = [
     {value: 'steak-0', viewValue: 'Steak'},

src/lib/select/select.spec.ts

@@ -244,8 +244,29 @@ describe('MdSelect', () => {
 
     beforeEach(() => {
       fixture = TestBed.createComponent(BasicSelect);
+    });
+
+    it('should take an initial view value with reactive forms', () => {
+      fixture.componentInstance.control = new FormControl('pizza-1');
+      fixture.detectChanges();
+
+      const value = fixture.debugElement.query(By.css('.md-select-value'));
+      expect(value.nativeElement.textContent)
+          .toContain('Pizza', `Expected trigger to be populated by the control's initial value.`);
+
+      trigger = fixture.debugElement.query(By.css('.md-select-trigger')).nativeElement;
+      trigger.click();
       fixture.detectChanges();
 
+      const options =
+          overlayContainerElement.querySelectorAll('md-option') as NodeListOf<HTMLElement>;
+      expect(options[1].classList)
+          .toContain('md-selected',
+              `Expected option with the control's initial value to be selected.`);
+    });
+
+    beforeEach(() => {
+      fixture.detectChanges();
       trigger = fixture.debugElement.query(By.css('.md-select-trigger')).nativeElement;
     });
 

src/lib/select/select.ts

@@ -5,6 +5,7 @@ import {
   ElementRef,
   EventEmitter,
   Input,
+  NgZone,
   OnDestroy,
   Optional,
   Output,
@@ -133,7 +134,8 @@ export class MdSelect implements AfterContentInit, ControlValueAccessor, OnDestr
   @Output() onClose = new EventEmitter();
 
   constructor(private _element: ElementRef, private _renderer: Renderer,
-              @Optional() private _dir: Dir, @Optional() public _control: NgControl) {
+              @Optional() private _dir: Dir, @Optional() public _control: NgControl,
+              private _ngZone: NgZone) {
     if (this._control) {
       this._control.valueAccessor = this;
     }
@@ -175,7 +177,14 @@ export class MdSelect implements AfterContentInit, ControlValueAccessor, OnDestr
    * required to integrate with Angular's core forms API.
    */
   writeValue(value: any): void {
-    if (!this.options) { return; }
+    if (!this.options) {
+      // In reactive forms, writeValue() will be called synchronously before
+      // the select's child options have been created. It's necessary to call
+      // writeValue() again after the options have been created to ensure any
+      // initial view value is set.
+      this._ngZone.onStable.first().subscribe(() => this.writeValue(value));
+      return;
+    }
 
     this.options.forEach((option: MdOption) => {
       if (option.value === value) {