[WebView Support Library] Support service worker APIs.
am: e149215027

Change-Id: Ib24a7ca9ae957f77ed5dbd9da7655b48eff2415d
tree: e5b3aae3f110003b36c1b2ffc7f730ee0624ca6b
  1. BUILD.gn
  2. DEPS
  3. proguard.flags
  4. src/