Make PrinterProviderAPI a pure interface

extensions/browser/api/printer_provider/printer_provider_api_factory.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 EXTENSIONS_BROWSER_API_PRINTER_PROVIDER_PRINTER_PROVIDER_API_FACTORY_H_
+#define EXTENSIONS_BROWSER_API_PRINTER_PROVIDER_PRINTER_PROVIDER_API_FACTORY_H_
+
+#include "base/lazy_instance.h"
+#include "base/macros.h"
+#include "components/keyed_service/content/browser_context_keyed_service_factory.h"
+
+class KeyedService;
+
+namespace content {
+class BrowserContext;
+}
+
+namespace extensions {
+class PrinterProviderAPI;
+}
+
+namespace extensions {
+
+// Factory for PrinterProviderAPI.
+class PrinterProviderAPIFactory : public BrowserContextKeyedServiceFactory {
+ public:
+  static PrinterProviderAPIFactory* GetInstance();
+
+  PrinterProviderAPI* GetForBrowserContext(content::BrowserContext* context);
+
+ private:
+  friend struct base::DefaultLazyInstanceTraits<PrinterProviderAPIFactory>;
+
+  PrinterProviderAPIFactory();
+  ~PrinterProviderAPIFactory() override;
+
+  // BrowserContextKeyedServiceFactory implementation:
+  KeyedService* BuildServiceInstanceFor(
+      content::BrowserContext* context) const override;
+  content::BrowserContext* GetBrowserContextToUse(
+      content::BrowserContext* context) const override;
+
+  DISALLOW_COPY_AND_ASSIGN(PrinterProviderAPIFactory);
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_BROWSER_API_PRINTER_PROVIDER_PRINTER_PROVIDER_API_FACTORY_H_