libbrillo: Update libchrome APIS to r456626.

The new libchrome has been ported from Chromium and some APIs have
changed. Make necessary changes at call sites.

Notable changes from libchrome:
- FOR_EACH_OBSERVER macro removed (replaced by use of C++ 11 range-base
  for loop)
- base::Values no more FundamentalValue
- stl_util moved to base namespace
- some scoped pointers removed in crypto/ in favor of BoringSSL
  UniquePtr.
- path() accessor renamed to GetPath() in ScopedTempDir (and other
  classes)

BUG: 37434548
Test: All tests in libbrillo_test pass on aosp_arm-eng build

Change-Id: Ibd2734bd83811feb93f24b1576a605eb33c3e645