Remove some PlatformFile instances from ChromeOS Drive.

chrome/browser/chromeos/drive/drive_file_stream_reader.cc

Index: chrome/browser/chromeos/drive/drive_file_stream_reader.cc
diff --git a/chrome/browser/chromeos/drive/drive_file_stream_reader.cc b/chrome/browser/chromeos/drive/drive_file_stream_reader.cc
index e9d97b115936e6803b274d78bb759b6c4b637f31..be4bd084a35f3c155df2ea0e0c1462464f48fba4 100644
--- a/chrome/browser/chromeos/drive/drive_file_stream_reader.cc
+++ b/chrome/browser/chromeos/drive/drive_file_stream_reader.cc
@@ -119,6 +119,9 @@ int LocalReaderProxy::Read(net::IOBuffer* buffer, int buffer_length,
     buffer_length = static_cast<int>(remaining_length_);
   }
 
+  if (!buffer_length)
+    return 0;
+
   file_reader_->Read(buffer, buffer_length,
                      base::Bind(&LocalReaderProxy::OnReadCompleted,
                                 weak_ptr_factory_.GetWeakPtr(), callback));