Ionic4.alpha2 item-sliding bug

gistfile1.txt

Ionic4.alpha2:  the avatar and button in the item-sliding will make the first rendering of the page very slow.

**Ionic version:**  (check one with "x")
(For Ionic 1.x issues, please use https://github.com/ionic-team/ionic-v1)
[ ] **2.x**
[ ] **3.x**
[x] **4.x**

**I'm submitting a ...**  (check one with "x")
[x] bug report
[ ] feature request

**Current behavior:**

The `ion-avatar` and `ion-button` in the `ion-item-sliding` will make the first rendering of the page very slow(about 4-5 minutes to render).


**Expected behavior:**
It should render immediately.

**Steps to reproduce:**

use the standard tabs demo.

**Related code:**

home.page.html:

```html
<ion-content padding>
  <ion-list>
    <ion-item-group>
      <ion-item-divider>Ha</ion-item-divider>
      <ion-item-sliding>
        <ion-item>
          <ion-avatar><img src="/assets/icon/favicon.png"/></ion-avatar>
          <ion-label>Tomy</ion-label>
          <ion-button slot="end">
            <ion-icon slot="icon-only" name="mail"></ion-icon>
          </ion-button>
        </ion-item>
        <ion-item-options>
          <ion-item-option>
            <ion-icon slot="icon-only" name="arrow-up"></ion-icon>
          </ion-item-option>
        </ion-item-options>
      </ion-item-sliding>
    </ion-item-group>
  </ion-list>
</ion-content>
```

**Other information:**

**Ionic info:** (run `ionic info` from a terminal/cmd prompt and paste output below):

```
   @ionic/cli-utils  : 2.0.0-rc.5
   ionic (Ionic CLI) : 4.0.0-rc.5

local packages:

   @angular-devkit/core       : 0.5.7
   @angular-devkit/schematics : 0.5.7
   @angular/cli               : 6.0.0-rc.6
   @ionic/schematics-angular  : 1.0.0-rc.5
   Ionic Framework            : @ionic/angular 4.0.0-alpha.2

System:

   NodeJS : v8.11.1
   npm    : 5.6.0
   OS     : Linux 4.15
```

screenshot1.png