Add FileSystemMountPointProvider::CreateFileReader() which returns appropriate Reader instance

webkit/fileapi/file_system_context.h

 // Copyright (c) 2012 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 WEBKIT_FILEAPI_FILE_SYSTEM_CONTEXT_H_
 #define WEBKIT_FILEAPI_FILE_SYSTEM_CONTEXT_H_
 
 #include <string>
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/platform_file.h"
 #include "webkit/fileapi/file_system_types.h"
 #include "webkit/quota/special_storage_policy.h"
 
 class FilePath;
 class GURL;
 
 namespace base {
 class MessageLoopProxy;
 }
 
 namespace quota {
 class QuotaManagerProxy;
 }
 
+namespace webkit_blob {
+class FileReader;
+}
+
 namespace fileapi {
 
 class ExternalFileSystemMountPointProvider;
 class FileSystemFileUtil;
 class FileSystemMountPointProvider;
 class FileSystemOperationInterface;
 class FileSystemOptions;
 class FileSystemPathManager;
 class FileSystemQuotaUtil;
 class IsolatedMountPointProvider;
@@ skipping 69 matching lines @@
 
   // Creates a new FileSystemOperation instance by cracking
   // the given filesystem URL |url| to get an appropriate MountPointProvider
   // and calling the provider's corresponding CreateFileSystemOperation method.
   // The resolved MountPointProvider could perform further specialization
   // depending on the filesystem type pointed by the |url|.
   FileSystemOperationInterface* CreateFileSystemOperation(
       const GURL& url,
       base::MessageLoopProxy* file_proxy);
 
+  // Creates new FileReader instance to read a file pointed by the given
+  // filesystem URL |url| starting from |offset|.
+  // This method internally cracks the |url|, get an appropriate
+  // MountPointProvider for the URL and call the provider's CreateFileReader.
+  // The resolved MountPointProvider could perform further specialization
+  // depending on the filesystem type pointed by the |url|.
+  webkit_blob::FileReader* CreateFileReader(
+      const GURL& url,
+      int64 offset,
+      base::MessageLoopProxy* file_proxy);
+
  private:
   friend struct DefaultContextDeleter;
   void DeleteOnCorrectThread() const;
 
   scoped_refptr<base::MessageLoopProxy> file_message_loop_;
   scoped_refptr<base::MessageLoopProxy> io_message_loop_;
 
   scoped_refptr<quota::QuotaManagerProxy> quota_manager_proxy_;
 
   // Mount point providers.
   scoped_ptr<SandboxMountPointProvider> sandbox_provider_;
   scoped_ptr<IsolatedMountPointProvider> isolated_provider_;
   scoped_ptr<ExternalFileSystemMountPointProvider> external_provider_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(FileSystemContext);
 };
 
 struct DefaultContextDeleter {
   static void Destruct(const FileSystemContext* context) {
     context->DeleteOnCorrectThread();
   }
 };
 
 }  // namespace fileapi
 
 #endif  // WEBKIT_FILEAPI_FILE_SYSTEM_CONTEXT_H_