Added brotli enc/ and tools/ directories.

third_party/brotli/enc/literal_cost.h

+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+// Literal cost model to allow backward reference replacement to be efficient.
+
+#ifndef BROTLI_ENC_LITERAL_COST_H_
+#define BROTLI_ENC_LITERAL_COST_H_
+
+#include "./types.h"
+
+namespace brotli {
+
+// Estimates how many bits the literals in the interval [pos, pos + len) in the
+// ringbuffer (data, mask) will take entropy coded and writes these estimates
+// to the cost[0..len) array.
+void EstimateBitCostsForLiterals(size_t pos, size_t len, size_t mask,
+                                 const uint8_t *data, float *cost);
+
+}  // namespace brotli
+
+#endif  // BROTLI_ENC_LITERAL_COST_H_