mat-select seems to have serious performance issue

#### Bug, feature request, or proposal:
With latest release, mat-form-field support was added for mat-select. But it introduced performance issues when we have multiple select lists (5-8).

When we use mat-form-field with input or text area it doesn't seem to cause any performance issue but it seem that its implementation for mat-select needs a review. On lengthy forms we are seeing a delay of up to 3 seconds, which are instant without mat-form-field on mat-select.

#### What is the expected behavior?
It should smooth and fast.

#### What is the current behavior?
Its very slow.

#### Which versions of Angular, Material, OS, TypeScript, browsers are affected?
Angular 4.4.4
Material 2.0.0-beta.12
Chrome

El informe menciona mat-select y mat-form-field, pero no indica archivos, pruebas ni un punto de entrada para la reproducción. Empieza reproduciendo el retraso reportado con 5–8 controles mat-select en Angular 4.4.4 y Material 2.0.0-beta.12; después, compáralo con mat-select sin mat-form-field. El trabajo estará terminado cuando el formulario extenso ya no muestre el retraso de varios segundos reportado y el comportamiento esté cubierto por una prueba de regresión o un benchmark.

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