Add ClearHistory() to ContentSuggestionsService and its providers

components/ntp_snippets/content_suggestions_service_unittest.cc

Index: components/ntp_snippets/content_suggestions_service_unittest.cc
diff --git a/components/ntp_snippets/content_suggestions_service_unittest.cc b/components/ntp_snippets/content_suggestions_service_unittest.cc
index bf3f4a4d321a653b19fc67daf6c7d918b5c16f74..39f5716c5437e0add925c5cfc115164480c4ae06 100644
--- a/components/ntp_snippets/content_suggestions_service_unittest.cc
+++ b/components/ntp_snippets/content_suggestions_service_unittest.cc
@@ -100,6 +100,7 @@ class MockProvider : public ContentSuggestionsProvider {
     observer()->OnSuggestionInvalidated(this, category, suggestion_id);
   }
 
+  MOCK_METHOD0(ClearHistory, void());
   MOCK_METHOD1(ClearCachedSuggestions, void(Category category));
   MOCK_METHOD2(GetDismissedSuggestionsForDebugging,
                void(Category category,
@@ -567,4 +568,11 @@ TEST_F(ContentSuggestionsServiceTest, ShouldPutBookmarksAtEndIfEmpty) {
   EXPECT_THAT(service()->GetCategories(), ElementsAre(remote, bookmarks));
 }
 
+TEST_F(ContentSuggestionsServiceTest, ShouldRemoveHistory) {

[Marc Treib, 2016/08/29 09:43:11]

ShouldForwardClearHistory? The service doesn't really do anything...

[vitaliii, 2016/08/29 10:37:25]

Done.

+  Category category = FromKnownCategory(KnownCategories::DOWNLOADS);
+  MockProvider* provider = RegisterProvider(category);
+  EXPECT_CALL(*provider, ClearHistory());
+  service()->ClearHistory();
+}
+
 }  // namespace ntp_snippets