Wait for scroll offset in testScrollPositionRestoring.

ios/web/shell/test/page_state_egtest.mm

Index: ios/web/shell/test/page_state_egtest.mm
diff --git a/ios/web/shell/test/page_state_egtest.mm b/ios/web/shell/test/page_state_egtest.mm
index dd11441d4baa2a30a1f2d26827f22fb95a5d6891..b8e9b09bd9061848768283aaefc37b9a5a4b678a 100644
--- a/ios/web/shell/test/page_state_egtest.mm
+++ b/ios/web/shell/test/page_state_egtest.mm
@@ -47,6 +47,29 @@
       nil);
 }
 
+// Waits for the web view scroll view is scrolled to |y_offset|.
+void WaitForOffset(CGFloat y_offset) {
+  CGPoint content_offset = CGPointMake(0.0, y_offset);
+  NSString* content_offset_string = NSStringFromCGPoint(content_offset);
+  NSString* name =
+      [NSString stringWithFormat:@"Wait for scroll view to scroll to %@.",
+                                 content_offset_string];
+  GREYCondition* condition = [GREYCondition
+      conditionWithName:name
+                  block:^BOOL {
+                    NSError* error = nil;
+                    [[EarlGrey
+                        selectElementWithMatcher:web::webViewScrollView()]
+                        assertWithMatcher:contentOffset(content_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);
+}
+
 }  // namespace
 
 using web::test::HttpServer;
@@ -60,10 +83,6 @@ @implementation PageStateTestCase
 // Tests that page scroll position of a page is restored upon returning to the
 // page via the back/forward buttons.
 - (void)testScrollPositionRestoring {
-  // TODO(crbug.com/670700): Re-enable this test.
-  if (!base::ios::IsRunningOnIOS10OrLater()) {
-    EARL_GREY_TEST_DISABLED(@"Test disabled on pre-iOS 10");
-  }
   web::test::SetUpFileBasedHttpServer();
 
   // Load first URL which is a long page.
@@ -87,12 +106,14 @@ - (void)testScrollPositionRestoring {
   // Go back and verify that the first page offset has been restored.
   [[EarlGrey selectElementWithMatcher:web::backButton()]
       performAction:grey_tap()];
+  WaitForOffset(kScrollOffset1);
   [[EarlGrey selectElementWithMatcher:web::webViewScrollView()]

[Eugene But (OOO till 7-30), 2017/01/18 18:36:02]

Do you still need this?

[kkhorimoto, 2017/01/18 18:44:47]

Nope

       assertWithMatcher:contentOffset(CGPointMake(0, kScrollOffset1))];
 
   // Go forward and verify that the second page offset has been restored.
   [[EarlGrey selectElementWithMatcher:web::forwardButton()]
       performAction:grey_tap()];
+  WaitForOffset(kScrollOffset2);
   [[EarlGrey selectElementWithMatcher:web::webViewScrollView()]

[Eugene But (OOO till 7-30), 2017/01/18 18:36:01]

ditto

[kkhorimoto, 2017/01/18 18:44:47]

Done.

       assertWithMatcher:contentOffset(CGPointMake(0, kScrollOffset2))];
 }