Fixed PageStateTest.testScrollPositionRestoring flake.

ios/web/shell/test/page_state_egtest.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 <CoreGraphics/CoreGraphics.h>
 #import <EarlGrey/EarlGrey.h>
 #import <Foundation/Foundation.h>
 #import <XCTest/XCTest.h>
 
 #include "base/ios/ios_util.h"
@@ skipping 35 matching lines @@
                         assertWithMatcher:grey_scrollViewContentOffset(offset)
                                     error:&error];
                     return (error == nil);
                   }];
   NSString* error_text =
       [NSString stringWithFormat:@"Scroll view did not scroll to %@",
                                  content_offset_string];
   GREYAssert([condition waitWithTimeout:10], error_text);
 }
 
+// Loads the long page at |url|, scrolls to the top, and waits for the offset to
+// be {0, 0} before returning.
+void LoadLongPageAndScrollToTop(const GURL& url) {

[Eugene But (OOO till 7-30), 2017/04/19 22:48:27]

"And" word in a method name is kind of a red flag. Could you please change it to
ScrollToTop.

[kkhorimoto, 2017/04/19 23:43:10]

Done.

+  // Load the page and swipe down.
+  [ShellEarlGrey loadURL:url];
+  [[EarlGrey selectElementWithMatcher:web::WebViewScrollView()]
+      performAction:grey_scrollToContentEdge(kGREYContentEdgeTop)];
+  // Waits for the {0, 0} offset.
+  WaitForOffset(0.0);
+}
+
 }  // namespace
 
 using web::test::HttpServer;
 
 // Page state test cases for the web shell.
 @interface PageStateTestCase : WebShellTestCase
 @end
 
 @implementation PageStateTestCase
 
 // Tests that page scroll position of a page is restored upon returning to the
 // page via the back/forward buttons.
-// TODO(crbug.com/702410): This test flakily fails when it scrolls too far down
-// the page.
-- (void)FLAKY_testScrollPositionRestoring {
+- (void)testScrollPositionRestoring {
   web::test::SetUpFileBasedHttpServer();
 
-  // Load first URL which is a long page.
-  [ShellEarlGrey loadURL:HttpServer::MakeUrl(kLongPage1)];
-
   // Scroll the first page and verify the offset.
+  LoadLongPageAndScrollToTop(HttpServer::MakeUrl(kLongPage1));
   [[EarlGrey selectElementWithMatcher:web::WebViewScrollView()]
       performAction:grey_scrollInDirection(kGREYDirectionDown, kOffset1)];
   [[EarlGrey selectElementWithMatcher:web::WebViewScrollView()]
       assertWithMatcher:grey_scrollViewContentOffset(CGPointMake(0, kOffset1))];
 
-  // Load second URL, which is also a long page.
-  [ShellEarlGrey loadURL:HttpServer::MakeUrl(kLongPage2)];
-
   // Scroll the second page and verify the offset.
+  LoadLongPageAndScrollToTop(HttpServer::MakeUrl(kLongPage2));
   [[EarlGrey selectElementWithMatcher:web::WebViewScrollView()]
       performAction:grey_scrollInDirection(kGREYDirectionDown, kOffset2)];
   [[EarlGrey selectElementWithMatcher:web::WebViewScrollView()]
       assertWithMatcher:grey_scrollViewContentOffset(CGPointMake(0, kOffset2))];
 
   // Go back and verify that the first page offset has been restored.
   [[EarlGrey selectElementWithMatcher:web::BackButton()]
       performAction:grey_tap()];
   WaitForOffset(kOffset1);
 
   // Go forward and verify that the second page offset has been restored.
   [[EarlGrey selectElementWithMatcher:web::ForwardButton()]
       performAction:grey_tap()];
   WaitForOffset(kOffset2);
 }
 
 @end