Add a unit test for the BookmarkSuggestionsProvider.

components/ntp_snippets/fake_content_suggestions_provider_observer.h

Index: components/ntp_snippets/fake_content_suggestions_provider_observer.h
diff --git a/components/ntp_snippets/fake_content_suggestions_provider_observer.h b/components/ntp_snippets/fake_content_suggestions_provider_observer.h
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index 0000000000000000000000000000000000000000..60ff2bf48a66aa07a9a420d46898178b7d357d26
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+++ b/components/ntp_snippets/fake_content_suggestions_provider_observer.h
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+// Copyright 2017 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.
+
+#ifndef COMPONENTS_NTP_SNIPPETS_FAKE_CONTENT_SUGGESTIONS_PROVIDER_OBSERVER_H_
+#define COMPONENTS_NTP_SNIPPETS_FAKE_CONTENT_SUGGESTIONS_PROVIDER_OBSERVER_H_
+
+#include <map>
+#include <vector>
+
+#include "base/macros.h"
+#include "components/ntp_snippets/category.h"
+#include "components/ntp_snippets/content_suggestion.h"
+#include "components/ntp_snippets/content_suggestions_provider.h"
+
+namespace ntp_snippets {
+
+class FakeContentSuggestionsProviderObserver
+    : public ContentSuggestionsProvider::Observer {
+ public:
+  FakeContentSuggestionsProviderObserver();
+  ~FakeContentSuggestionsProviderObserver();
+
+  void OnNewSuggestions(ContentSuggestionsProvider* provider,
+                        Category category,
+                        std::vector<ContentSuggestion> suggestions) override;
+
+  void OnCategoryStatusChanged(ContentSuggestionsProvider* provider,
+                               Category category,
+                               CategoryStatus new_status) override;
+
+  void OnSuggestionInvalidated(
+      ContentSuggestionsProvider* provider,
+      const ContentSuggestion::ID& suggestion_id) override;
+
+  const std::map<Category, CategoryStatus, Category::CompareByID>& statuses()
+      const;
+
+  CategoryStatus StatusForCategory(Category category) const;
+
+  const std::vector<ContentSuggestion>& SuggestionsForCategory(
+      Category category);
+
+ private:
+  std::map<Category, CategoryStatus, Category::CompareByID> statuses_;
+  std::map<Category, std::vector<ContentSuggestion>, Category::CompareByID>
+      suggestions_;
+
+  DISALLOW_COPY_AND_ASSIGN(FakeContentSuggestionsProviderObserver);
+};
+
+}  // namespace ntp_snippets
+
+#endif  // COMPONENTS_NTP_SNIPPETS_FAKE_CONTENT_SUGGESTIONS_PROVIDER_OBSERVER_H_