Allow cross dependencies between BCKSF and BSKSF

components/keyed_service/ios/browser_state_context_converter.h

+// Copyright 2014 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_KEYED_SERVICE_IOS_BROWSER_STATE_CONTEXT_CONVERTER_H_
+#define COMPONENTS_KEYED_SERVICE_IOS_BROWSER_STATE_CONTEXT_CONVERTER_H_
+
+#include "base/macros.h"
+
+namespace base {
+class SupportsUserData;
+}
+
+// BrowserStateContextConverter does safe conversion of base::SupportsUserData*
+// to web::BrowserState* or content::BrowserContext*.
+//
+// iOS code is still using BrowserContextKeyedServiceFactory and until the
+// conversion is complete — http://crbug.com/478763 — there is need to have
+// mixed dependency between BCKSF and BSKSF.
+//
+// The implementation has BrowserStateKeyedServiceFactory supporting a
+// BrowserContextDependencyManager as DependencyManager. Thus the context
+// parameter passed to the BrowserStateKeyedServiceFactory can either be
+// content::BrowserContext if the method is invoked by DependencyManager
+// or web::BrowserState if the method is invoked via the type-safe public
+// API.
+//
+// The public API of BrowserStateKeyedServiceFactory is type-safe (all
+// public method receive web::BrowserState for context object), so only
+// methods that take a base::SupportsUserData need to discriminate
+// between the two objects.
+class BrowserStateContextConverter {
+ public:
+  // Sets/Gets the global BrowserStateContextConverter instance. May return null
+  // when mixed dependencies are disabled.
+  static void SetInstance(BrowserStateContextConverter* instance);
+  static BrowserStateContextConverter* GetInstance();
+
+  // Converts |context| to a web::BrowserState* and returns it casted as a
+  // base::SupportsUserData*.
+  virtual base::SupportsUserData* GetBrowserStateForContext(
+      base::SupportsUserData* context) = 0;
+  // Converts |context| to a content::BrowserContext* and returns it casted as a
+  // base::SupportsUserData*.
+  virtual base::SupportsUserData* GetBrowserContextForContext(
+      base::SupportsUserData* context) = 0;
+
+ protected:
+  BrowserStateContextConverter();
+  virtual ~BrowserStateContextConverter();
+
+  DISALLOW_COPY_AND_ASSIGN(BrowserStateContextConverter);
+};
+
+#endif  // COMPONENTS_KEYED_SERVICE_IOS_BROWSER_STATE_CONTEXT_CONVERTER_H_