[iOS] Only verify error code when link tapping fails.

The behavior of TapWebViewElementWithId() for links that close a
WebState is flaky on both simulator and device, regardless of whether
the Phase 1 UI Reboot flag is enabled.  This CL updates
FullscreenTestCase.testShowHeaderWhenChildTabCloses to check for the
error code only if the link tap is unsuccessful.

Note that the closure of the Tab and the visibility of the toolbar is
still verified after this occurs, so the test will still catch
fullscreen regressions after this change.

Bug: 812664
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: Ia56293763e185eeb615a5f734aa9a3a473f0b424
Reviewed-on: https://chromium-review.googlesource.com/974791
Commit-Queue: Kurt Horimoto <kkhorimoto@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Reviewed-by: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#545713}

ios/chrome/browser/ui/fullscreen/fullscreen_egtest.mm

@@ -4,6 +4,7 @@
 
 #import <EarlGrey/EarlGrey.h>
 #import <UIKit/UIKit.h>
+#import <WebKit/WebKit.h>
 #import <XCTest/XCTest.h>
 
 #include "base/ios/ios_util.h"
@@ -247,11 +248,6 @@ void AssertURLIs(const GURL& expectedURL) {
 // Test to make sure the header is shown when a Tab opened by the current Tab is
 // closed even if the toolbar was not present previously.
 - (void)testShowHeaderWhenChildTabCloses {
-// TODO(crbug.com/812664): Re-enable this test on devices.
-#if !TARGET_IPHONE_SIMULATOR
-  EARL_GREY_TEST_DISABLED(@"Test disabled on device.");
-#endif
-
   std::map<GURL, std::string> responses;
   const GURL URL = web::test::HttpServer::MakeUrl("http://origin");
   const GURL destinationURL =
@@ -297,22 +293,18 @@ void AssertURLIs(const GURL& expectedURL) {
   HideToolbarUsingUI();
   [ChromeEarlGreyUI waitForToolbarVisible:NO];
 
-  // Close the tab.
+  // Close the tab by tapping link2.
   NSError* error = nil;
-  bool success = chrome_test_util::TapWebViewElementWithId("link2", &error);
-
-  if (!web::GetWebClient()->IsSlimNavigationManagerEnabled()) {
-    // The effect of clicking the link, closes the tab and invalidates the web
-    // view. This results in |TapWebViewElementWithId| returning false. This
-    // error is represented by code 3. WKBasedNavigationManager does not trigger
-    // any error.
-    GREYAssertFalse(success, @"Failed to tap \"link2\"");
-    GREYAssert(error.code == 3,
+  if (!chrome_test_util::TapWebViewElementWithId("link2", &error)) {
+    // Sometimes, the tap will be unsuccessful due to the window.close()
+    // operation invalidating the WKWebView.  If this occurs, verify the error.
+    // This results in |TapWebViewElementWithId| returning false.
+    // TODO(crbug.com/824879): Remove conditional once flake is eliminated from
+    // TapWebViewElementWithId() for window.close() links.
+    GREYAssert(error.code == WKErrorWebViewInvalidated,
                @"Failed to receive WKErrorWebViewInvalidated error");
-    GREYAssert([error.domain isEqualToString:@"WKErrorDomain"],
+    GREYAssert([error.domain isEqualToString:WKErrorDomain],
                @"Failed to receive WKErrorDomain error");
-  } else {
-    GREYAssert(success, @"Failed to tap \"link2\"");
   }
 
   [ChromeEarlGrey waitForWebViewContainingText:"link1"];