Split HistoryClient in two objects

chrome/browser/history/chrome_history_backend_client.h

+// 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.
+
+#ifndef CHROME_BROWSER_HISTORY_CHROME_HISTORY_BACKEND_CLIENT_H_
+#define CHROME_BROWSER_HISTORY_CHROME_HISTORY_BACKEND_CLIENT_H_
+
+#include "base/macros.h"
+#include "components/history/core/browser/history_backend_client.h"
+
+namespace bookmarks {
+class BookmarkModel;
+}
+
+// ChromeHistoryBackendClient implements history::HistoryBackendClient interface
+// to provides access to embedder-specific features.
+class ChromeHistoryBackendClient : public history::HistoryBackendClient {
+ public:
+  explicit ChromeHistoryBackendClient(bookmarks::BookmarkModel* bookmark_model);
+  ~ChromeHistoryBackendClient() override;
+
+  // history::HistoryBackendClient implementation.
+  bool IsBookmarked(const GURL& url) override;
+  void GetBookmarks(std::vector<history::URLAndTitle>* bookmarks) override;
+  bool ShouldReportDatabaseError() override;
+#if defined(OS_ANDROID)
+  void OnHistoryBackendInitialized(
+      history::HistoryBackend* history_backend,
+      history::HistoryDatabase* history_database,
+      history::ThumbnailDatabase* thumbnail_database,
+      const base::FilePath& history_dir) override;
+  void OnHistoryBackendDestroyed(history::HistoryBackend* history_backend,
+                                 const base::FilePath& history_dir) override;
+#endif  // defined(OS_ANDROID)
+
+ private:
+  // BookmarkModel instance providing access to bookmarks. May be null during
+  // testing but must outlive ChromeHistoryBackendClient if non-null.
+  bookmarks::BookmarkModel* bookmark_model_;
+
+  DISALLOW_COPY_AND_ASSIGN(ChromeHistoryBackendClient);
+};
+
+#endif  // CHROME_BROWSER_HISTORY_CHROME_HISTORY_BACKEND_CLIENT_H_