Add a unit test for the BookmarkSuggestionsProvider.

components/ntp_snippets/BUILD.gn

Index: components/ntp_snippets/BUILD.gn
diff --git a/components/ntp_snippets/BUILD.gn b/components/ntp_snippets/BUILD.gn
index fc9837331b04e67cfdb52d4cb5209ad72bb5a2ee..1bac0cf5bae060e3d52cf17e9ecd3b5e62d70632 100644
--- a/components/ntp_snippets/BUILD.gn
+++ b/components/ntp_snippets/BUILD.gn
@@ -129,6 +129,7 @@ source_set("unit_tests") {
   testonly = true
   sources = [
     "bookmarks/bookmark_last_visit_utils_unittest.cc",
+    "bookmarks/bookmark_suggestions_provider_unittest.cc",
     "category_rankers/click_based_category_ranker_unittest.cc",
     "category_rankers/constant_category_ranker_unittest.cc",
     "category_unittest.cc",
@@ -184,6 +185,10 @@ source_set("test_support") {
     "category_rankers/fake_category_ranker.h",
     "category_rankers/mock_category_ranker.cc",
     "category_rankers/mock_category_ranker.h",
+    "fake_content_suggestions_provider_observer.cc",
+    "fake_content_suggestions_provider_observer.h",
+    "mock_content_suggestions_provider.cc",
+    "mock_content_suggestions_provider.h",
     "mock_content_suggestions_provider_observer.cc",
     "mock_content_suggestions_provider_observer.h",
     "offline_pages/offline_pages_test_utils.cc",
@@ -196,5 +201,6 @@ source_set("test_support") {
     "//components/offline_pages/core",
     "//components/offline_pages/core:test_support",
     "//testing/gmock",
+    "//testing/gtest",
   ]
 }