fix: delay on-load sanity checks

Delays the sanity checks from the `CompatibilityModule` by 5 seconds, in order to give the user's base styles a better chance to load.

Fixes #4125.

Author: crisbeto

src/lib/core/compatibility/compatibility.ts

@@ -7,6 +7,7 @@ import {
   Optional,
   isDevMode,
   ElementRef,
+  NgZone,
 } from '@angular/core';
 import {DOCUMENT} from '@angular/platform-browser';
 import {MdError} from '../errors/error';
@@ -193,11 +194,16 @@ export class CompatibilityModule {
     };
   }
 
-  constructor(@Optional() @Inject(DOCUMENT) private _document: any) {
+  constructor(@Optional() @Inject(DOCUMENT) private _document: any, ngZone: NgZone) {
     if (!hasDoneGlobalChecks && isDevMode()) {
-      this._checkDoctype();
-      this._checkTheme();
-      hasDoneGlobalChecks = true;
+      ngZone.runOutsideAngular(() => {
+        // Delay running the check to allow more time for the user's styles to load.
+        setTimeout(() => {
+          this._checkDoctype();
+          this._checkTheme();
+          hasDoneGlobalChecks = true;
+        }, 5000);
+      });
     }
   }