[Feed] Add a parameterized artificial delay legacy NTP.

(cherry picked from commit 6e988a738d51630cef1492c1a959821404bef5ab)

Bug: 968217
Change-Id: I97f4470edcf170a94e084ab208046be2024633b7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1646973
Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Theresa <twellington@chromium.org>
Commit-Queue: Sky Malice <skym@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#668453}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1665474
Reviewed-by: Sky Malice <skym@chromium.org>
Cr-Commit-Position: refs/branch-heads/3809@{#432}
Cr-Branched-From: d82dec1a818f378c464ba307ddd9c92133eac355-refs/heads/master@{#665002}

• chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java[diff]
• chrome/android/junit/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapterTest.java[diff]
• tools/metrics/histograms/histograms.xml[diff]