Make Isolated file system writable only if it is configured so

webkit/fileapi/file_system_operation.cc

 // 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.
 
 #include "webkit/fileapi/file_system_operation.h"
 
 #include "base/bind.h"
 #include "base/sequenced_task_runner.h"
 #include "base/time.h"
 #include "base/utf_string_conversions.h"
@@ skipping 269 matching lines @@
     const WriteCallback& callback) {
   DCHECK(SetPendingOperationType(kOperationWrite));
 
   base::PlatformFileError result = SetUpFileSystemPath(
       path_url, &src_path_, &src_util_, PATH_FOR_WRITE);
   if (result != base::PLATFORM_FILE_OK) {
     callback.Run(result, 0, false);
     delete this;
     return;
   }
+
+  FileSystemMountPointProvider* provider = file_system_context()->
+      GetMountPointProvider(src_path_.type());
+  DCHECK(provider);
+  scoped_ptr<FileStreamWriter> writer(provider->CreateFileStreamWriter(
+          path_url, offset, file_system_context()));
+
+  if (!writer.get()) {
+    // Write is not supported.
+    callback.Run(base::PLATFORM_FILE_ERROR_SECURITY, 0, false);
+    delete this;
+    return;
+  }
+
   DCHECK(blob_url.is_valid());
   file_writer_delegate_.reset(new FileWriterDelegate(
       base::Bind(&FileSystemOperation::DidWrite, weak_factory_.GetWeakPtr()),
-      scoped_ptr<FileStreamWriter>(
-          new SandboxFileStreamWriter(file_system_context(),
-                                      path_url,
-                                      offset))));
+      writer.Pass()));
+
   set_write_callback(callback);
   scoped_ptr<net::URLRequest> blob_request(
       new net::URLRequest(blob_url, file_writer_delegate_.get()));
   blob_request->set_context(url_request_context);
 
   file_writer_delegate_->Start(blob_request.Pass());
 }
 
 void FileSystemOperation::Truncate(const GURL& path_url, int64 length,
                                    const StatusCallback& callback) {
@@ skipping 408 matching lines @@
 }
 
 bool FileSystemOperation::SetPendingOperationType(OperationType type) {
   if (pending_operation_ != kOperationNone)
     return false;
   pending_operation_ = type;
   return true;
 }
 
 }  // namespace fileapi