Merge third_party/brotli/src from https://chromium.googlesource.com/external/font-compression-reference.git at 931479d735e1121548c3b07aec866fd772cc4932

This commit was generated by merge_from_chromium.py.

Change-Id: I0ce348d2a5ef41ea7bd5d2361fa096a634e209f0