No automated tests possible.

Manual test on iPhone7:
- on a page with no back session history, swiping should not trigger
any haptics.
- on a page where you can go back, a small blip should be felt each time
the activation threshold is crossed, before you lift your finger.
- Upon releasing to trigger the back action, an additional stronger blip
should be felt.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6ea20a431c457a98f0de01ce0de4c020a15714b6

commit 6ea20a431c457a98f0de01ce0de4c020a15714b6
Author: pinkerton <pinkerton@chromium.org>
Date: Thu Feb 23 17:21:55 2017

Add haptic feedback for swipe-to-go-back.

For supporting devices (iPhone7), provide haptic feedback when the
user successfully triggers the back/forward action. Also pulse slightly
each time the user crosses the activation threshold.

Also moves haptic trigger routines into uikit_util.h and fixes up
the Overscroll code to use these shared functions.

BUG= 695137 
TEST=See https://bugs.chromium.org/p/chromium/issues/detail?id=695137#c1 for manual test details.

Review-Url: https://codereview.chromium.org/2709233003
Cr-Commit-Position: refs/heads/master@{#452531}

[modify] https://crrev.com/6ea20a431c457a98f0de01ce0de4c020a15714b6/ios/chrome/browser/ui/overscroll_actions/overscroll_actions_controller.mm
[modify] https://crrev.com/6ea20a431c457a98f0de01ce0de4c020a15714b6/ios/chrome/browser/ui/side_swipe/side_swipe_navigation_view.mm
[modify] https://crrev.com/6ea20a431c457a98f0de01ce0de4c020a15714b6/ios/chrome/browser/ui/uikit_ui_util.h
[modify] https://crrev.com/6ea20a431c457a98f0de01ce0de4c020a15714b6/ios/chrome/browser/ui/uikit_ui_util.mm

Verified in 58.0.3026.0 canary, iPhone 7 iOS 10.2.1

Haptic feedback is felt when triggering the back/forward action by swiping. Also pulse slightly each time the user crosses the activation threshold.

Tested for websites with history sessions, pull-to-refresh (swipe down action).