Implement ClearHistory for all ntp_snippets providers

components/ntp_snippets/ntp_snippets_service.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/ntp_snippets/ntp_snippets_service.h"
 
 #include <algorithm>
 #include <iterator>
 #include <utility>
 
@@ skipping 321 matching lines @@
   database_->LoadImage(
       snippet_id,
       base::Bind(&NTPSnippetsService::OnSnippetImageFetchedFromDatabase,
                  base::Unretained(this), callback, snippet_id));
 }
 
 void NTPSnippetsService::ClearHistory(
     base::Time begin,
     base::Time end,
     const base::Callback<bool(const GURL& url)>& filter) {
-  // TODO(vitaliii): Implement. See crbug.com/641321.
+  // Note that both time range and the filter are ignored and all suggestions
+  // are removed, because it is not known which history entries were used for
+  // the suggestions personalization.
+  if (!ready())
+    nuke_after_load_ = true;
+  else
+    NukeAllSnippets();

[Marc Treib, 2016/09/01 14:11:20]

Since this four-line block now exists twice, we could put it into its own helper
method. Not sure what a good name would be though...

[vitaliii, 2016/09/01 14:45:15]

Acknowledged.

 }
 
 void NTPSnippetsService::ClearCachedSuggestions(Category category) {
   DCHECK_EQ(category, provided_category_);
   if (!initialized())
     return;
 
   if (snippets_.empty())
     return;
 
@@ skipping 546 matching lines @@
 void NTPSnippetsService::UpdateCategoryStatus(CategoryStatus status) {
   if (status == category_status_)
     return;
 
   category_status_ = status;
   observer()->OnCategoryStatusChanged(this, provided_category_,
                                       category_status_);
 }
 
 }  // namespace ntp_snippets