[change] StyleSheet.hairlineWidth is whole pixel value

Even on high DPI screens, browsers can round sub-pixel values down to
`0`. This causes hairlineWidth borders/heights/etc not to be rendered.
Revert `hairlineWidth` value back to `1`.

packages/react-native-web/src/exports/StyleSheet/StyleSheet.js

@@ -10,7 +10,6 @@
 import StyleSheetValidation from './StyleSheetValidation';
 import ReactNativePropRegistry from '../../modules/ReactNativePropRegistry';
 import flattenStyle from './flattenStyle';
-import getHairlineWidth from './getHairlineWidth';
 
 const absoluteFillObject = {
   position: 'absolute',
@@ -43,7 +42,7 @@ const StyleSheet = {
     return result;
   },
   flatten: flattenStyle,
-  hairlineWidth: getHairlineWidth()
+  hairlineWidth: 1
 };
 
 export default StyleSheet;

packages/react-native-web/src/exports/StyleSheet/getHairlineWidth.js

@@ -1,25 +0,0 @@
-/**
- * Based on http://dieulot.net/css-retina-hairline
- * @noflow
- */
-
-import { canUseDOM } from 'fbjs/lib/ExecutionEnvironment';
-
-const getHairlineWidth = () => {
-  let hairlineWidth = 1;
-  if (canUseDOM && window.devicePixelRatio && window.devicePixelRatio >= 2) {
-    const body = document.body;
-    if (body) {
-      const node = document.createElement('div');
-      node.style.border = '.5px solid transparent';
-      body.appendChild(node);
-      if (node.offsetHeight === 1) {
-        hairlineWidth = 0.5;
-      }
-      body.removeChild(node);
-    }
-  }
-  return hairlineWidth;
-};
-
-export default getHairlineWidth;