Merge third_party/brotli/src from https://chromium.googlesource.com/external/font-compression-reference.git at dfc5a9f2151a7c88914c236c7db8fa119fee249c

This commit was generated by merge_from_chromium.py.

Change-Id: Ia04f2b3241d465f54b5f57c92c478560f8aa3e51