A separate setting ("Show Content Suggestions") is added to Settings->Privacy.
This setting controls the remote suggestions ("Articles for You"). If the switch is on, the suggestions are shown normally.
If it is off, no suggestions are shown and currently displayed suggestions are removed.
On opening a new NTP, the section should be empty.
The Reading List section is unaffected by this setting.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f55c6b19bfe0f477948551a632974fb90bcf6943

commit f55c6b19bfe0f477948551a632974fb90bcf6943
Author: gambard <gambard@chromium.org>
Date: Wed Aug 02 15:45:16 2017

Have a settings to opt out of ContentSuggestions

The user needs to be able to opt out of Content Suggestions if needed.
Android is coupling the Omnibox suggestions and the Content suggestions
setting but it is probably clearer to have it separated.
However the names are misleading and need to be changed.

TEST= Toggle the switch Settings->Privacy->"Show Content Suggestions".
- When enabled the suggestions are shown as expected.
- When disabled, the remote suggestions("Articles for You") currently
  displayed are removed.
  When opening a new NTP the Articles for You section is empty.
The Reading List section is unaffected.

Bug:  751623 
Change-Id: I076f2f25697741e6f351a90da500a6ef33b21bf1
Reviewed-on: https://chromium-review.googlesource.com/598069
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Eric Noyau <noyau@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491384}
[modify] https://crrev.com/f55c6b19bfe0f477948551a632974fb90bcf6943/ios/chrome/app/strings/ios_strings.grd
[modify] https://crrev.com/f55c6b19bfe0f477948551a632974fb90bcf6943/ios/chrome/browser/ntp_snippets/ios_chrome_content_suggestions_service_factory_util.cc
[modify] https://crrev.com/f55c6b19bfe0f477948551a632974fb90bcf6943/ios/chrome/browser/pref_names.cc
[modify] https://crrev.com/f55c6b19bfe0f477948551a632974fb90bcf6943/ios/chrome/browser/pref_names.h
[modify] https://crrev.com/f55c6b19bfe0f477948551a632974fb90bcf6943/ios/chrome/browser/prefs/browser_prefs.mm
[modify] https://crrev.com/f55c6b19bfe0f477948551a632974fb90bcf6943/ios/chrome/browser/ui/content_suggestions/content_suggestions_collection_updater.mm
[modify] https://crrev.com/f55c6b19bfe0f477948551a632974fb90bcf6943/ios/chrome/browser/ui/settings/privacy_collection_view_controller.mm

When I tested this, I still saw a message about suggested articles and the "learn more" link when content suggestions were disabled. I think they shouldn't be shown and these messages are hidden on Android with suggestions disabled. What do you think about this? 

Yes, we are discussing what to do with the empty section and the "Learn more" link on crbug.com/753342

Verified in 62.0.3179.0 canary, iPhone 6 iOS 10.3.3, iPhone 7 iOS11, iPad Pro iOS11

1. Go to Settings->Privacy
2. Turn OFF 'Articles suggestions'

No suggestions are shown. But the Title 'Articles for you', 'That's all for now...' and More link are still shown crbug.com/753342.