Fix testContextMenuOpenInNewTabFromTallPage.

ios/chrome/browser/context_menu/context_menu_egtest.mm

Index: ios/chrome/browser/context_menu/context_menu_egtest.mm
diff --git a/ios/chrome/browser/context_menu/context_menu_egtest.mm b/ios/chrome/browser/context_menu/context_menu_egtest.mm
index 3e021534098550e68294ad48c4449e43f494ca20..f65f1cf156085adfcbd5b399a1508e3479763355 100644
--- a/ios/chrome/browser/context_menu/context_menu_egtest.mm
+++ b/ios/chrome/browser/context_menu/context_menu_egtest.mm
@@ -189,9 +189,7 @@ void SelectTabAtIndexInCurrentMode(NSUInteger index) {
 // Tests "Open in New Tab" on context menu  on a link that requires scrolling
 // on the page to verify that context menu can be properly triggered in the
 // current screen view.
-// TODO(crbug.com/701104): This test is flaky because sometimes it doesn't
-// scroll down far enough for the link to be visible.
-- (void)FLAKY_testContextMenuOpenInNewTabFromTallPage {
+- (void)testContextMenuOpenInNewTabFromTallPage {
   // Set up test simple http server.
   std::map<GURL, std::string> responses;
   GURL initialURL =
@@ -211,10 +209,19 @@ void SelectTabAtIndexInCurrentMode(NSUInteger index) {
   chrome_test_util::AssertMainTabCount(1U);
 
   // Scroll down on the web view to make the link visible.
+  // grey_swipeFastInDirecton will quickly scroll towards the bottom, and then
+  // grey_scrollToContentEdge guarantees the content edge is reached. Two
+  // methods are used because the first one is much faster, but doesn't
+  // guarantee the link becomes visible.
   [[EarlGrey
       selectElementWithMatcher:WebViewScrollView(
                                    chrome_test_util::GetCurrentWebState())]
       performAction:grey_swipeFastInDirection(kGREYDirectionUp)];
+  [[EarlGrey
+      selectElementWithMatcher:WebViewScrollView(
+                                   chrome_test_util::GetCurrentWebState())]
+      performAction:grey_scrollToContentEdge(kGREYContentEdgeBottom)];

[Eugene But (OOO till 7-30), 2017/03/16 16:54:52]

It's pretty bad that |grey_scrollToContentEdge| is so slow that callers have to
use |grey_swipeFastInDirection| first. Do you want to file a bug against EG and
add a TODO to clean this up?

[baxley, 2017/03/16 17:05:14]

Done.
Yeah, I agree that it's so slow. For a lot of tests it can be fine to just use
that, but this is a really long webpage. I filed a bug to track this, and I'll
reply to the existing EG issue about this to see if they want to do that. The
downside is it adds even more scroll/swipe APIs, but it doesn't hurt to address
it.

+
   [[EarlGrey selectElementWithMatcher:chrome_test_util::WebViewContainingText(
                                           kDestinationLinkID)]
       assertWithMatcher:grey_notNil()];