Create ShareableFileReference on IO thread

webkit/fileapi/file_system_file_util.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_FILE_UTIL_H_
 #define WEBKIT_FILEAPI_FILE_SYSTEM_FILE_UTIL_H_
 
 #include "base/file_path.h"
 #include "base/file_util_proxy.h"
 #include "base/memory/ref_counted.h"
@@ skipping 28 matching lines @@
     virtual ~AbstractFileEnumerator() {}
 
     // Returns an empty string if there are no more results.
     virtual FilePath Next() = 0;
 
     virtual int64 Size() = 0;
     virtual base::Time LastModifiedTime() = 0;
     virtual bool IsDirectory() = 0;
   };
 
+  // A policy flag for CreateSnapshotFile.
+  enum SnapshotFilePolicy {
+    kSnapshotFileUnknown,
+
+    // The implementation just uses the local file as the snapshot file.
+    // The FileAPI backend does nothing on the returned file.
+    kSnapshotFileLocal,
+
+    // The implementation returns a temporary file as the snapshot file.
+    // The FileAPI backend takes care of the lifetime of the returned file
+    // and will delete when the last reference of the file is dropped.
+    kSnapshotFileTemporary,
+  };
+
   class EmptyFileEnumerator : public AbstractFileEnumerator {
     virtual FilePath Next() OVERRIDE { return FilePath(); }
     virtual int64 Size() OVERRIDE { return 0; }
     virtual base::Time LastModifiedTime() OVERRIDE { return base::Time(); }
     virtual bool IsDirectory() OVERRIDE { return false; }
   };
 
   virtual ~FileSystemFileUtil() {}
 
   // Creates or opens a file with the given flags.
@@ skipping 117 matching lines @@
       const FileSystemURL& url) = 0;
 
   // Creates a local snapshot file for a given |url| and returns the
   // metadata and platform path of the snapshot file via |callback|.
   // In regular filesystem cases the implementation may simply return
   // the metadata of the file itself (as well as GetMetadata does),
   // while in non-regular filesystem case the backend may create a
   // temporary snapshot file which holds the file data and return
   // the metadata of the temporary file.
   //
-  // |result| is the return code of the operation.
   // |file_info| is the metadata of the snapshot file created.
   // |platform_path| is the path to the snapshot file created.
-  //
-  // The implementation can optionally return a file reference
-  // to let the fileapi backend manage the lifetime of the returned
-  // snapshot file. Otherwise it is ok to return NULL.
-  // Please see the comment for ShareableFileReference for details.
-  virtual scoped_refptr<webkit_blob::ShareableFileReference>
-      CreateSnapshotFile(FileSystemOperationContext* context,
-                         const FileSystemURL& url,
-                         base::PlatformFileError* result,
-                         base::PlatformFileInfo* file_info,
-                         FilePath* platform_path) = 0;
+  // |policy| should indicate the policy how the fileapi backend
+  // should handle the returned file.
+  virtual base::PlatformFileError CreateSnapshotFile(
+      FileSystemOperationContext* context,
+      const FileSystemURL& url,
+      base::PlatformFileInfo* file_info,
+      FilePath* platform_path,
+      SnapshotFilePolicy* policy) = 0;
 
  protected:
   FileSystemFileUtil() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FileSystemFileUtil);
 };
 
 }  // namespace fileapi
 
 #endif  // WEBKIT_FILEAPI_FILE_SYSTEM_FILE_UTIL_H_