platform2: Fix issues with new version of libchrome

libchrome r334380 has the following breaking changes that need to be fixed:
- base::JSONWriter::Write() and base::JSONWriter::WriteWithOptions() take
  "const base::Value&" instead of "const base::Value*"
- base::JSONReader::Read() and base::JSONReader::ReadAndReturnError()
  return a scoped_ptr<base::Value> instead of base::Value*
- base/safe_strerror_posix.h is moved to base/posix/safe_strerror.h
- safe_strerror() is now in "base" namespace
- StartsWithASCII(), EndsWith(), StringToUpperASCII(), LowerCaseEqualsASCII()
  are now in "base" namespace
- ObserverList<T> is now in "base" namespace
- base::PrintTo(base::FilePath) used in gtest is now moved to libchrome-test
  library and as such, unit test runners need to link to this library now.
- crypto::RSAPrivateKey::CreateSensitive() is now removed from //crypto, so
  some of tests in chromeos-login that used that function had to be changed
  to use crypto::GenerateRSAKeyPairNSS() directly.
- UnixDomanSocket class is now in "base" namespace
- Pickle class is now in "base" namespace

BUG=chromium:496469
TEST=`./build_packages`
CQ-DEPEND=CL:277662

Change-Id: I36e5fbf2e36a92068873ffbd44020c862a3ed9e3
Reviewed-on: https://chromium-review.googlesource.com/277671


Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
Trybot-Ready: Alex Vakulenko <avakulenko@chromium.org>
Tested-by: Alex Vakulenko <avakulenko@chromium.org>