fix(form-field): allow for measuring outline gap when label is not in…

… dom

src/lib/form-field/form-field.ts

@@ -141,6 +141,7 @@ export const MAT_FORM_FIELD_DEFAULT_OPTIONS =
 export class MatFormField extends _MatFormFieldMixinBase
     implements AfterContentInit, AfterContentChecked, AfterViewInit, CanColor {
   private _labelOptions: LabelOptions;
+  private _outlineGapCalculationNeeded = false;
 
   /** The form-field appearance style. */
   @Input()
@@ -300,6 +301,9 @@ export class MatFormField extends _MatFormFieldMixinBase
 
   ngAfterContentChecked() {
     this._validateControlChild();
+    if (this._outlineGapCalculationNeeded) {
+      this.updateOutlineGap();
+    }
   }
 
   ngAfterViewInit() {
@@ -448,6 +452,13 @@ export class MatFormField extends _MatFormFieldMixinBase
       return;
     }
 
+    // If the element is not present in the DOM, the outline gap will need to be calculated
+    // the next time it is checked and in the DOM.
+    if (document && !document.documentElement.contains(this._elementRef.nativeElement)) {
+      this._outlineGapCalculationNeeded = true;
+      return;
+    }
+
     let startWidth = 0;
     let gapWidth = 0;
     const startEls = this._connectionContainerRef.nativeElement.querySelectorAll<HTMLElement>(
@@ -459,9 +470,6 @@ export class MatFormField extends _MatFormFieldMixinBase
         // getBoundingClientRect isn't available on the server.
         return;
       }
-      if (!document.documentElement.contains(this._elementRef.nativeElement)) {
-        return;
-      }
 
       const containerStart = this._getStartEnd(
           this._connectionContainerRef.nativeElement.getBoundingClientRect());
@@ -481,6 +489,8 @@ export class MatFormField extends _MatFormFieldMixinBase
     for (let i = 0; i < gapEls.length; i++) {
       gapEls.item(i).style.width = `${gapWidth}px`;
     }
+
+    this._outlineGapCalculationNeeded = false;
   }
 
   /** Gets the start end of the rect considering the current directionality. */