window.open calls do not provide any information about syntheticClickType or position in WKNavigationAction's description. Improvements will only be possible iff https://bugs.webkit.org/show_bug.cgi?id=142106 is fixed. rdar://19989909

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/068fb4c73610a31db8066ad92d83aaeb51060e71

commit 068fb4c73610a31db8066ad92d83aaeb51060e71
Author: Eugene But <eugenebut@chromium.org>
Date: Mon May 21 21:48:34 2018

Improve user gesture detection for target=_blank link activations.

It is possible to reliably tell if link was activated with or
without user gesture via GetNavigationActionInitiationType().
This CL remove fallback to [self userIsInteracting] heuristic.

Updated all link click tests to use real tap events, instead
of JavaScript clicks.

Added testLinkWithBlankTargetWithoutUserGesture test to verify
that JavaScript link click popups are blocked.

Bug: 809706
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I2811513c0e160b29e20fb0d69ae3ceed316a9653
Reviewed-on: https://chromium-review.googlesource.com/1066773
Commit-Queue: Eugene But <eugenebut@chromium.org>
Reviewed-by: Mohammad Refaat <mrefaat@chromium.org>
Cr-Commit-Position: refs/heads/master@{#560347}
[modify] https://crrev.com/068fb4c73610a31db8066ad92d83aaeb51060e71/ios/chrome/browser/web/window_open_by_dom_egtest.mm
[modify] https://crrev.com/068fb4c73610a31db8066ad92d83aaeb51060e71/ios/web/web_state/ui/crw_web_controller.mm