This reverts commit ab640662.

Reason for revert: ArticleSnippetsTest has failed consistently
on KitKat Tablet Tester since this landed. Specifically the
following tests are failing:
  ArticleSnippetsTest#testDownloadSuggestion__ChromeHomeEnabled
  ArticleSnippetsTest#testSigninPromo__ChromeHomeEnabled
  ArticleSnippetsTest#testSnippetAppearance__ChromeHomeEnabled

Additionally, many other test suites that follow
chrome_public_test_apk started failing when this landed; not
sure if that's related.

Original change's description:
> Render snippets in ArticleSnippetsTest in isolation
> 
> Remove the "snippets" render that shows all cards together, because
> multiple, non-article sections are not realistic in the modern design
> anymore.
> 
> Rebaseline other renders:
> * Use relative timestamp instead of Jan 17, 1970
> * Use only single-card backgrounds for pre-modern cards
> * Update modern card background color after https://crrev.com/497799
> * Update pre-modern text color after https://crrev.com/500684
> 
> Also move card contents in the modern layout except for the rounded
> corners into a RelativeLayout, to avoid a circular dependency between
> the height of the containing layout and the position of the bottom
> corner (see https://developer.android.com/reference/android/widget/RelativeLayout.html).
> 
> Bug: 757735
> Change-Id: I81add3d5bdd8ffec61b9e8aa2ff3a9caa44ccf91
> Reviewed-on: https://chromium-review.googlesource.com/628562
> Commit-Queue: Bernhard Bauer <bauerb@chromium.org>
> Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
> Reviewed-by: Juan Antonio Navarro Pérez <perezju@chromium.org>
> Reviewed-by: Peter Conn <peconn@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#500975}

TBR=bauerb@chromium.org,skyostil@chromium.org,perezju@chromium.org,peconn@chromium.org

Change-Id: Iedb4e042448a8e4c8090d8af5fbdbb6e2f19a6b7
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 757735
Reviewed-on: https://chromium-review.googlesource.com/663382Reviewed-by: John Mellor <johnme@chromium.org>
Commit-Queue: John Mellor <johnme@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501269}