Fix testWebViewIsFirstResponderUponKeyPress for iOS 11.3+

This CL fixes the testWebViewIsFirstResponderUponKeyPress test which was
failing for iOS 11.3+. The changes in iOS 11.3+ is that the WKWebView is
the first responder instead of the WKContentView.

Bug: 830124, 837564
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I9b5c343579657c5db9d3973820e5c67ae495bcb4
Reviewed-on: https://chromium-review.googlesource.com/1052008Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557169}

ios/chrome/browser/ui/keyboard_commands_egtest.mm

@@ -200,10 +200,16 @@ using chrome_test_util::SettingsDoneButton;
   [self verifyKeyboardCommandsAreRegistered];
 
   UIResponder* firstResponder = GetFirstResponder();
-  GREYAssert(
-      [firstResponder isKindOfClass:NSClassFromString(@"WKContentView")],
-      @"Expected first responder to be a WKContentView. Instead, is a %@",
-      NSStringFromClass([firstResponder class]));
+  if (@available(iOS 11.3, *)) {
+    GREYAssert([firstResponder isKindOfClass:NSClassFromString(@"WKWebView")],
+               @"Expected first responder to be a WKWebView. Instead, is a %@",
+               NSStringFromClass([firstResponder class]));
+  } else {
+    GREYAssert(
+        [firstResponder isKindOfClass:NSClassFromString(@"WKContentView")],
+        @"Expected first responder to be a WKContentView. Instead, is a %@",
+        NSStringFromClass([firstResponder class]));
+  }
 }
 
 @end