Github uses https://github.com/licensee/licensee to detect which
license a project uses. licensee doesn't currently detect Perfetto's
license. By trial and error this seems to be because we put part of
the license at the top that is normally at the bottom:

Before:
➜  2020-04-20-license git:(master) ✗ bundle exec bin/licensee detect ../../src/perfetto/LICENSE
License:        NOASSERTION
Matched files:  LICENSE
LICENSE:
  Content hash:  805f77a38d4cfd1c37aabca8f208f13d4b1b9d0d
  License:       NOASSERTION
  Closest non-matching licenses:
    ECL-2.0 similarity:  96.67%

After:
➜  2020-04-20-license git:(master) ✗ bundle exec bin/licensee detect ../../src/perfetto/LICENSE
License:        Apache-2.0
Matched files:  LICENSE
LICENSE:
  Content hash:  ab3901051663cb8ee5dea9ebdff406ad136910e3
  Confidence:    100.00%
  Matcher:       Licensee::Matchers::Exact
  License:       Apache-2.0

Change-Id: I6a3d78d3b6350a12c1a1790fbb7a61ac3f36fcd6