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

webkit/fileapi/isolated_mount_point_provider.h

Index: webkit/fileapi/isolated_mount_point_provider.h
diff --git a/webkit/fileapi/isolated_mount_point_provider.h b/webkit/fileapi/isolated_mount_point_provider.h
index c6be4fcce9688872b5fea59b0437ba81a3c4ac0f..141bc94d5f71eb326d4d1d5db98c8a7de929e8d4 100644
--- a/webkit/fileapi/isolated_mount_point_provider.h
+++ b/webkit/fileapi/isolated_mount_point_provider.h
@@ -47,6 +47,11 @@ class IsolatedMountPointProvider : public FileSystemMountPointProvider {
       const FilePath& virtual_path,
       base::MessageLoopProxy* file_proxy,
       FileSystemContext* context) const OVERRIDE;
+  virtual webkit_blob::FileReader* CreateFileReader(
+    const GURL& url,
+    int64 offset,
+    base::MessageLoopProxy* file_proxy,
+    FileSystemContext* context) const OVERRIDE;
 
  private:
   IsolatedContext* isolated_context() const;