Add helpers to swipe up and down on the current web view.

ios/chrome/test/earl_grey/chrome_earl_grey_ui.mm

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/chrome/test/earl_grey/chrome_earl_grey_ui.h"
 
 #include "ios/chrome/browser/ui/tools_menu/tools_menu_constants.h"
 #import "ios/chrome/browser/ui/uikit_ui_util.h"
 #import "ios/chrome/test/app/chrome_test_util.h"
 #include "ios/chrome/test/app/navigation_test_util.h"
@@ skipping 61 matching lines @@
 }
 
 + (void)openShareMenu {
   if (IsCompact()) {
     [ChromeEarlGreyUI openToolsMenu];
   }
   [[EarlGrey selectElementWithMatcher:chrome_test_util::ShareButton()]
       performAction:grey_tap()];
 }
 
++ (void)swipeUpOnWebView {
+  [[EarlGrey
+      selectElementWithMatcher:WebViewScrollView(
+                                   chrome_test_util::GetCurrentWebState())]
+      performAction:grey_swipeFastInDirection(kGREYDirectionUp)];
+}
+
++ (void)swipeDownOnWebView {
+  [[EarlGrey
+      selectElementWithMatcher:WebViewScrollView(
+                                   chrome_test_util::GetCurrentWebState())]
+      performAction:grey_swipeFastInDirection(kGREYDirectionDown)];
+}
+
 @end