Increase tolerance for receiver's certificate expiry

Increase the maximum allowed remaining lifetime for the
receiver's self-signed cert to 4 days.

This is being increased from 2 days because errors are
being seen in the field because of sender clocks being off.

In the future, we might find a way to warn the user that
their clock might be off, but for now just changing the
tolerance seems the right approach.

BUG=467736

R=mfoltz@chromium.org

Review URL: https://codereview.chromium.org/1011133005

Cr-Commit-Position: refs/heads/master@{#322497}

extensions/browser/api/cast_channel/cast_socket.cc

@@ -45,7 +45,7 @@
 
 namespace {
 
-const int kMaxSelfSignedCertLifetimeInDays = 2;
+const int kMaxSelfSignedCertLifetimeInDays = 4;
 
 std::string FormatTimeForLogging(base::Time time) {
   base::Time::Exploded exploded_time;
@@ -197,7 +197,7 @@ bool CastSocketImpl::ExtractPeerCert(std::string* cert) {
   logger_->LogSocketEvent(channel_id_, proto::SSL_INFO_OBTAINED);
 
   // Ensure that the peer cert (which is self-signed) doesn't have an excessive
-  // life-time (i.e. no more than 2 days).
+  // remaining life-time.
   base::Time expiry = ssl_info.cert->valid_expiry();
   base::Time lifetimeLimit =
       base::Time::Now() +