Revert "Fix #13983. Switch to //# for sourcemaps."

Per the discussion here:
https://code.google.com/p/chromium/issues/detail?id=256636

Thanks to the Chrome team for the quick response!

This reverts commit d53ddc90c1f119fb9148a553443ef3fbc3f3cc99.
(cherry picked from commit 6e630fbbb19306e1914712502a2b22872e94ddad)
Change the changelog header style
(cherry picked from commit a44202dc604d14688756ae0cccde0fec53e53dbf)