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

webkit/fileapi/file_system_mount_point_provider.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_MOUNT_POINT_PROVIDER_H_
 #define WEBKIT_FILEAPI_FILE_SYSTEM_MOUNT_POINT_PROVIDER_H_
 
 #include <string>
 #include <vector>
 
 #include "base/callback_forward.h"
 #include "base/file_path.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/platform_file.h"
 #include "webkit/fileapi/file_system_types.h"
 
 class GURL;
 
 namespace base {
 class MessageLoopProxy;
 }
 
+namespace webkit_blob {
+class FileReader;
+}
+
 namespace fileapi {
 
 class FileSystemContext;
 class FileSystemFileUtil;
 class FileSystemOperationInterface;
 class RemoteFileSystemProxyInterface;
 
 // An interface to provide mount-point-specific path-related utilities
 // and specialized FileSystemFileUtil instance.
 class FileSystemMountPointProvider {
@@ skipping 50 matching lines @@
   // mount point based on the given triplet of |origin_url|, |file_system_type|
   // and |virtual_path|.
   // This method is usually dispatched by
   // FileSystemContext::CreateFileSystemOperation.
   virtual FileSystemOperationInterface* CreateFileSystemOperation(
       const GURL& origin_url,
       FileSystemType file_system_type,
       const FilePath& virtual_path,
       base::MessageLoopProxy* file_proxy,
       FileSystemContext* context) const = 0;
+
+  // Creates a new file reader for a given filesystem URL |url| with a offset
+  // |offset|.
+  // The returned object must be owned and managed by the caller.
+  // This method itself does *not* check if the given path exists and is a
+  // regular file.
+  virtual webkit_blob::FileReader* CreateFileReader(
+    const GURL& url,
+    int64 offset,
+    base::MessageLoopProxy* file_proxy,
+    FileSystemContext* context) const = 0;
 };
 
 // An interface to control external file system access permissions.
 class ExternalFileSystemMountPointProvider
     : public FileSystemMountPointProvider {
  public:
   // Grant access to all external file system from extension identified with
   // |extension_id|.
   virtual void GrantFullAccessToExtension(const std::string& extension_id) = 0;
   // Grants access to |virtual_path| from |origin_url|.
@@ skipping 15 matching lines @@
   virtual void RemoveMountPoint(const FilePath& mount_point) = 0;
   // Gets virtual path by known filesystem path. Returns false when filesystem
   // path is not exposed by this provider.
   virtual bool GetVirtualPath(const FilePath& file_system_path,
                               FilePath* virtual_path) = 0;
 };
 
 }  // namespace fileapi
 
 #endif  // WEBKIT_FILEAPI_FILE_SYSTEM_MOUNT_POINT_PROVIDER_H_