fix(select): incorrect menu width when there is no placeholder

The select pane's width wasn't being set properly, when it doesn't have a placeholder, because the width usually gets set within the placeholder's setter.

Fixes angular#3244.

src/lib/select/select.spec.ts

@@ -38,7 +38,8 @@ describe('MdSelect', () => {
         FloatPlaceholderSelect,
         SelectWithErrorSibling,
         ThrowsErrorOnInit,
-        BasicSelectOnPush
+        BasicSelectOnPush,
+        BasicSelectNoPlaceholder
       ],
       providers: [
         {provide: OverlayContainer, useFactory: () => {
@@ -119,13 +120,27 @@ describe('MdSelect', () => {
     }));
 
     it('should set the width of the overlay based on the trigger', async(() => {
-      trigger.style.width = '200px';
-
       fixture.whenStable().then(() => {
         trigger.click();
         fixture.detectChanges();
+
+        const pane = overlayContainerElement.querySelector('.cdk-overlay-pane') as HTMLElement;
+        expect(pane.style.minWidth).toBe(trigger.getBoundingClientRect().width + 'px');
+      });
+    }));
+
+    it('should set the width of the overlay if there is no placeholder', async(() => {
+      let noPlaceholder = TestBed.createComponent(BasicSelectNoPlaceholder);
+
+      noPlaceholder.detectChanges();
+      trigger = noPlaceholder.debugElement.query(By.css('.mat-select-trigger')).nativeElement;
+
+      noPlaceholder.whenStable().then(() => {
+        trigger.click();
+        noPlaceholder.detectChanges();
+
         const pane = overlayContainerElement.querySelector('.cdk-overlay-pane') as HTMLElement;
-        expect(pane.style.minWidth).toBe('200px');
+        expect(parseInt(pane.style.minWidth)).toBeGreaterThan(0);
       });
     }));
 
@@ -1588,6 +1603,16 @@ class FloatPlaceholderSelect {
   @ViewChild(MdSelect) select: MdSelect;
 }
 
+@Component({
+  selector: 'basic-select-no-placeholder',
+  template: `
+    <md-select>
+      <md-option value="value">There are no other options</md-option>
+    </md-select>
+  `
+})
+class BasicSelectNoPlaceholder { }
+
 
 /**
  * TODO: Move this to core testing utility until Angular has event faking

src/lib/select/select.ts

@@ -257,6 +257,11 @@ export class MdSelect implements AfterContentInit, ControlValueAccessor, OnDestr
   ngAfterContentInit() {
     this._initKeyManager();
 
+    // If there is no placeholder, the setter won't fire so we need to trigger it from here.
+    if (!this._placeholder) {
+      this._triggerWidth = this._getWidth();
+    }
+
     this._changeSubscription = this.options.changes.startWith(null).subscribe(() => {
       this._resetOptions();