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

Il report menziona mat-select e mat-form-field, ma non indica file, test o un punto di ingresso per la riproduzione. Inizia riproducendo il ritardo segnalato con 5–8 controlli mat-select usando Angular 4.4.4 e Material 2.0.0-beta.12, quindi confrontalo con mat-select senza mat-form-field. Il lavoro è completato quando il modulo lungo non mostra più il ritardo di diversi secondi segnalato e il comportamento è coperto da un test di regressione o da un benchmark.

Scritto dal modello di indicizzazione a partire dal testo della issue.