title: angular material mat-autocomplete issues
body: <p>i am having a input box with mat-autocomplete. there is a search button that i hit to get the matching entries to populate the suggestions. Though overall it works but the behavior is bit annoying. This is what happens:</p>
  
  <ol>
  <li>I type ra and hit enter.</li>
  <li>after while the progress indicator returns and i see no other visual changes.</li>
  <li><p>if i hit down or right arrow etc i see no suggestions</p></li>
  <li><p>if i delete the last character then it shows the suggestions.</p></li>
  </ol>
  
  <p>the ui code looks like:</p>
  
  <pre><code>&lt;div fxLayout="row" fxLayoutAlign="start center"&gt;
        &lt;div&gt;
          &lt;form &gt;
              &lt;mat-form-field &gt;
                  &lt;input type="text" placeholder="Opportunity name" aria-label="Number" matInput [formControl]="myControl" [matAutocomplete]="auto"&gt;
                  &lt;mat-autocomplete #auto="matAutocomplete" [displayWith]="displayFn"&gt;
                  &lt;mat-option *ngFor="let option of filteredOptions | async" [value]="option"&gt;
                      {{ option.name }}
                  &lt;/mat-option&gt;
                  &lt;/mat-autocomplete&gt;
              &lt;/mat-form-field&gt; 
              &lt;/form&gt;
        &lt;/div&gt;
        &lt;div&gt;&amp;nbsp;&lt;mat-icon (click)="refreshOptyList()"&gt;search&lt;/mat-icon&gt;
        &lt;/div&gt;  
  
    &lt;/div&gt;
  </code></pre>
  
  <p>the refreshOptyList function is as follow:</p>
  
  <pre><code>refreshOptyList(){
         this.diaRef = this.dialog.open(MessageDialogComponent, {
            width: '250px',
            disableClose: true,
            data: { "message": "Please wait...", "showProgress": true }
       });
  
        this.revSvc.getOptyList(this.keyword).then(
          (val:any) =&gt; {
                          this.diaRef.close()
                          this.optyArr = JSON.parse(val._body).items;
  
                          for(let op of this.optyArr){
                            this.options.push(new Opty(op.Name, op.OptyNumber))
                          }
                       }
        )
  
    }
  </code></pre>