test(webkit): uncomment fixed viewport screenshot tests (#1346)

Author: pavelfeldman

test/golden-webkit/screenshot-element-mobile.png

@@ -179,7 +179,7 @@ module.exports.describe = function({testRunner, expect, product, FFOX, CHROMIUM,
       expect(screenshot).toBeGolden('screenshot-mobile-clip.png');
       await context.close();
     });
-    it.skip(FFOX).fail(WEBKIT)('should work with a mobile viewport and fullPage', async({browser, server}) => {
+    it.skip(FFOX)('should work with a mobile viewport and fullPage', async({browser, server}) => {
       const context = await browser.newContext({viewport: { width: 320, height: 480, isMobile: true }});
       const page = await context.newPage();
       await page.goto(server.PREFIX + '/overflow-large.html');
@@ -376,7 +376,7 @@ module.exports.describe = function({testRunner, expect, product, FFOX, CHROMIUM,
       const screenshot = await elementHandle.screenshot();
       expect(screenshot).toBeGolden('screenshot-element-fractional.png');
     });
-    it.skip(FFOX).fail(WEBKIT)('should work with a mobile viewport', async({browser, server}) => {
+    it.skip(FFOX)('should work with a mobile viewport', async({browser, server}) => {
       const context = await browser.newContext({viewport: { width: 320, height: 480, isMobile: true }});
       const page = await context.newPage();
       await page.goto(server.PREFIX + '/grid.html');