Remove parent* arg from GDataEntry ctor.

* Remove static FromDocumentEntry from GDataEntry, GDataFile, GDataDirectory. Replace with InitFromDocumentEntry.
* Move common code from GDataFile::InitFromDocumentEntry and GDataDirectory::InitFromDocumentEntry to GDataEntry::InitFromDocumentEntry.
* Add GDataDirectoryService::FromDocumentEntry and use this everywhere.
* Make ctors of GDataFile, GDataDirectory private, so these must be created by GDataDirectoryService's CreateGDataFile and
CreateGDataDirectory. Make GDataEntry ctor protected.

BUG=141494
TEST=unit tests.
Review URL: https://chromiumcodereview.appspot.com/10854083

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@151008 0039d316-1c4b-4281-b951-d872f2087c98
void GDataFileSystem::OnCloseFileFinished(
    const FilePath& file_path,
    const FileOperationCallback& callback,
    GDataFileError result) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));

  open_files_.erase(file_path);

  if (!callback.is_null())
    callback.Run(result);
}

void GDataFileSystem::OnCloseFileFinished(
    const FilePath& file_path,
    const FileOperationCallback& callback,
    GDataFileError result) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));

  open_files_.erase(file_path);

  if (!callback.is_null())
    callback.Run(result);
}
