perf(button): no reflows on button onInit

ionic/components/button/button.ts

@@ -1,30 +1,64 @@
-import {Directive} from 'angular2/angular2';
+import {Directive, ElementRef, Renderer} from 'angular2/angular2';
+
+import {IonicConfig} from '../../config/config';
 
 
 /**
  * TODO
  */
 @Directive({
-  selector: 'button,[button]',
-  host: {
-    '[class.icon-left]': 'iconLeft',
-    '[class.icon-right]': 'iconRight',
-    '[class.icon-only]': 'iconOnly'
-  }
+  selector: 'button,[button]'
 })
 export class Button {
 
-  constructor() {
+  constructor(
+    config: IonicConfig,
+    elementRef: ElementRef,
+    renderer: Renderer
+  ) {
     this.iconLeft = this.iconRight = this.iconOnly = false;
+
+    if (config.setting('hoverCSS') === false) {
+      renderer.setElementClass(elementRef, 'disable-hover', true);
+    }
+
+    // figure out if and where the icon lives in the button
+    let childNodes = elementRef.nativeElement.childNodes;
+    let childNode;
+    let nodes = [];
+    for (let i = 0, l = childNodes.length; i < l; i++) {
+      childNode = childNodes[i];
+      if (childNode.nodeType === 3) {
+        // text node
+        if (childNode.textContent.trim() !== '') {
+          nodes.push(TEXT);
+        }
+
+      } else if (childNode.nodeName === 'ICON') {
+        // element node
+        nodes.push(ICON);
+
+      } else {
+        // element other than an <icon>
+        nodes.push(TEXT);
+
+      }
+    }
+
+    if (nodes.length > 1) {
+      if (nodes[0] === ICON && nodes[1] === TEXT) {
+        renderer.setElementClass(elementRef, 'icon-left', true);
+
+      } else if (nodes[0] === TEXT && nodes[1] === ICON) {
+        renderer.setElementClass(elementRef, 'icon-right', true);
+      }
+    } else if (nodes.length === 1 && nodes[0] === ICON) {
+      renderer.setElementClass(elementRef, 'icon-only', true);
+    }
+
   }
 
-  /**
-   * TODO
-   * @param {TODO} icon  TODO
-   */
-  registerIcon(icon) {
-    this.iconLeft = icon.iconLeft;
-    this.iconRight = icon.iconRight;
-    this.iconOnly = icon.iconOnly;
-  }
 }
+
+const TEXT = 1;
+const ICON = 2;