Extract some Lottie::Animation code to Lottie::Player.

Telegram/SourceFiles/lottie/lottie_common.cpp

@@ -0,0 +1,30 @@
+/*
+This file is part of Telegram Desktop,
+the official desktop application for the Telegram messaging service.
+
+For license and copyright information please follow this link:
+https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
+*/
+#include "lottie/lottie_common.h"
+
+#include "base/algorithm.h"
+
+#include <QFile>
+
+namespace Lottie {
+namespace {
+
+QByteArray ReadFile(const QString &filepath) {
+	auto f = QFile(filepath);
+	return (f.size() <= kMaxFileSize && f.open(QIODevice::ReadOnly))
+		? f.readAll()
+		: QByteArray();
+}
+
+} // namespace
+
+QByteArray ReadContent(const QByteArray &data, const QString &filepath) {
+	return data.isEmpty() ? ReadFile(filepath) : base::duplicate(data);
+}
+
+} // namespace Lottie