GData downloads cleanup.

* Fix a leak in GDataFileSystem::OnTransferCompleted. 
* UploadCompletionCallback's returns an UploadFileInfo* (to enable it to be deleted) instead of DocumentEntry* 
* Split GDataUploader::RemovePendingUpload into UploadFailed and DeleteUpload. Make DeleteUpload public for use by GDataFileSystem::OnTransferCompleted.
* GDataUploader::UploadFile takes a scoped_ptr to make the transfer of ownership clearer.
* Rename GDataUploader::UploadComplete to GDataUploader::MoveFileToCache.
* Rename GDataDownloadObserver::temp_download_path_ to gdata_tmp_download_path_ for consistency with code elsewhere.
* Rearrange args in GDataDownloadObserver::Initialize
* Some other renames
* Get rid of gdata:: in gdata_file_system.cc
* pragma once in all header files.

BUG=NONE
TEST=NONE
Review URL: https://chromiumcodereview.appspot.com/9844006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@129595 0039d316-1c4b-4281-b951-d872f2087c98