Fix certificate checker callback lifetime.

OpenSSL's SSL_CTX_set_verify() function allows us to set a callback
called after certificate validation but doesn't provide a way to pass
private data to this callback. CL:183832 was passing the pointer to the
CertificateChecker instance using a global pointer, nevertheless the
lifetime of this pointer was wrong since libcurl can trigger this
callback asynchronously when the SSL certificates are downloaded.

This patch converts the CertificateChecker into a singleton class and
uses the same trick previously used to pass the ServerToCheck value
using different callbacks.

Bug: 25818567
Test: Run an update on edison-userdebug; FEATURES=test emerge-link update_engine

Change-Id: I84cdb2f8c5ac86d1463634e73e867f213f7a2f5a

0 files changed, 0 insertions, 0 deletions