The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a28b69512499272a8fc5e50798ecd040718dcf41

commit a28b69512499272a8fc5e50798ecd040718dcf41
Author: gambard <gambard@chromium.org>
Date: Mon Jul 03 12:14:51 2017

Modify ContentSuggestions scrolling behavior

As ContentSuggestions is displayed on the NTP, the scrolling behavior
should change. Here is the new behavior:
- Remove the scrolling bump between the omnibox being in the middle of
  the screen and being pinned at the top. The user can now scroll and
  let the omnibox in the middle of the screen, like Android.
- Upon focusing the omnibox, if it is not pinned to top, pin it.
- Upon unfocusing the omnibox, if it was moved (pinned) on focus, move
  the scroll to the position it had before the pinning.
- When scrolling up or down, unfocus the omnibox if it was focused,
  but let the scrolling go through to the collection.
- When tapping, unfocus the omnibox and let the tap go through (do
  nothing if there is no element, open the element if there is one).

Video: https://drive.google.com/open?id=0B21N-0pPGAuJYVl3a3hWay1kUHM

BUG= 737931 

Change-Id: Idf570abe5c9a44c9e73deb896369c437e661f628
Reviewed-on: https://chromium-review.googlesource.com/558059
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Louis Romero <lpromero@chromium.org>
Cr-Commit-Position: refs/heads/master@{#483993}
[modify] https://crrev.com/a28b69512499272a8fc5e50798ecd040718dcf41/ios/chrome/browser/ui/content_suggestions/BUILD.gn
[modify] https://crrev.com/a28b69512499272a8fc5e50798ecd040718dcf41/ios/chrome/browser/ui/content_suggestions/content_suggestions_collection_utils.mm
[modify] https://crrev.com/a28b69512499272a8fc5e50798ecd040718dcf41/ios/chrome/browser/ui/content_suggestions/content_suggestions_header_synchronizer.mm
[modify] https://crrev.com/a28b69512499272a8fc5e50798ecd040718dcf41/ios/chrome/browser/ui/content_suggestions/content_suggestions_view_controller.mm
[delete] https://crrev.com/853a46cde856de187f916e7b56734a7bba821b36/ios/chrome/browser/ui/content_suggestions/content_suggestions_view_controller_utils.h
[delete] https://crrev.com/853a46cde856de187f916e7b56734a7bba821b36/ios/chrome/browser/ui/content_suggestions/content_suggestions_view_controller_utils.mm
[delete] https://crrev.com/853a46cde856de187f916e7b56734a7bba821b36/ios/chrome/browser/ui/content_suggestions/content_suggestions_view_controller_utils_unittest.mm