Adds imageWriterPrivate support for Windows

chrome/browser/extensions/api/image_writer_private/write_from_file_operation.cc

Index: chrome/browser/extensions/api/image_writer_private/write_from_file_operation.cc
diff --git a/chrome/browser/extensions/api/image_writer_private/write_from_file_operation.cc b/chrome/browser/extensions/api/image_writer_private/write_from_file_operation.cc
index 65d845759a00190181f185827594be3f7b10aba4..f22895474386d269501cef9de7ae2fbfef62d070 100644
--- a/chrome/browser/extensions/api/image_writer_private/write_from_file_operation.cc
+++ b/chrome/browser/extensions/api/image_writer_private/write_from_file_operation.cc
@@ -25,15 +25,15 @@ WriteFromFileOperation::~WriteFromFileOperation() {
 }
 
 void WriteFromFileOperation::Start() {
-  DVLOG(1) << "Starting file-to-usb write of " << image_path_.value()
-           << " to " << storage_unit_id_;
-
   if (!base::PathExists(image_path_) || base::DirectoryExists(image_path_)) {
     Error(error::kImageInvalid);
     return;
   }
 
-  WriteStart();
+  BrowserThread::PostTask(
+      BrowserThread::FILE,
+      FROM_HERE,
+      base::Bind(&WriteFromFileOperation::WriteStart, this));
 }
 
 }  // namespace image_writer