move hairline shim to bootstrap

ionic/components/app/app.ts

@@ -110,6 +110,22 @@ export class IonicApp {
       }
     });
 
+    /**
+    * Hairline Shim
+    * Add the "hairline" CSS class name to the body tag
+    * if the browser supports subpixels.
+    */
+    if (window.devicePixelRatio >= 2) {
+      var hairlineEle = document.createElement('div');
+      hairlineEle.style.border = '.5px solid transparent';
+      document.body.appendChild(hairlineEle);
+
+      if (hairlineEle.offsetHeight === 1) {
+        document.body.classList.add('hairlines');
+      }
+      document.body.removeChild(hairlineEle);
+    }
+
     bodyEle.setAttribute('mode', config.setting('mode'));
   }