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 CopyLocalFileOnBlockingPool(
    const FilePath& src_file_path,
    const FilePath& dest_file_path,
    GDataFileError* error) {
  DCHECK(error);

  *error = file_util::CopyFile(src_file_path, dest_file_path) ?
      GDATA_FILE_OK : GDATA_FILE_ERROR_FAILED;
}

void CopyLocalFileOnBlockingPool(
    const FilePath& src_file_path,
    const FilePath& dest_file_path,
    GDataFileError* error) {
  DCHECK(error);

  *error = file_util::CopyFile(src_file_path, dest_file_path) ?
      GDATA_FILE_OK : GDATA_FILE_ERROR_FAILED;
}
