Revert of Add per-section clearing and dismissed suggestions to snippets-internals

Revert of Add per-section clearing and dismissed suggestions to snippets-internals (patchset #3 id:40001 of https://codereview.chromium.org/2222853004/ )

Reason for revert:
Reverting this CL because it breaks the following bot: https://build.chromium.org/p/chromium.linux/builders/Android%20Builder/builds/70928

Original issue's description:
> Add per-section clearing and dismissed suggestions to snippets-internals
> 
> Add new ClearCachedSuggestionsForDebugging,
> GetDismissedSuggestionsForDebugging and
> ClearDismissedSuggestionsForDebugging methods to the
> ContentSuggestionsProvider. Implement these methods in all existing
> providers. Adjust the unit tests.
> 
> Call those methods from snippets-internals, build new internals UI for
> viewing dismissed suggestions and clearing suggestions per category.
> Remove now unused NTPSnippetsService-related things.
> 
> BUG=619560
> CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation
> 
> Committed: https://crrev.com/17361590f84745a69e0373e6482184e3bada6c3b
> Cr-Commit-Position: refs/heads/master@{#410360}

TBR=treib@chromium.org,bauerb@chromium.org,pke@google.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=619560

[anthonyvd, 2016-08-08 15:48:34]

The CQ bit was checked by anthonyvd@chromium.org

[anthonyvd, 2016-08-08 15:48:35]

Created Revert of Add per-section clearing and dismissed suggestions to
snippets-internals

[commit-bot: I haz the power, 2016-08-08 15:49:04]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-08-08 15:50:12]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-08-08 15:50:14]

Failed to apply the patch.