Update libchromiumcontent to get on Chrome Stable channel

This reverts many parts of be62b66f9a11660610ef08e6cd65d4f669d71e7f.

* vendor/libchromiumcontent f4f8a7e...a7e28c5 (12):
  > Export SQLitePersistentCookieStore's constructor on Windows
  > Fix Windows linker errors in skia_opts[_ssse3]
  > Fix linker errors about use of content:: symbols in browser_net
  > Revert "Update V8 target names"
  > Pull in the fix for http://crbug.com/234342
  > Revert "Stop trying to compile SQLitePersistentCookieStore separately"
  > Remove patches that aren't needed for Chrome 27
  > Fix DomStorageHost patch to apply against Chrome 27
  > Update custom_deps to match latest recommendations
  > Build the latest stable channel release of Chromium
  > Merge pull request #18 from brightray/encryptor
  > Merge pull request #17 from brightray/cygwin