Provide method for returning certificate expiration timestamp.

webrtc/base/timeutils.h

Index: webrtc/base/timeutils.h
diff --git a/webrtc/base/timeutils.h b/webrtc/base/timeutils.h
index bdeccc3739263721ed33d9635e035d0b9f9cdfb8..3ade43094708c92e02e075522a4da151b7712059 100644
--- a/webrtc/base/timeutils.h
+++ b/webrtc/base/timeutils.h
@@ -11,6 +11,7 @@
 #ifndef WEBRTC_BASE_TIMEUTILS_H_
 #define WEBRTC_BASE_TIMEUTILS_H_
 
+#include <ctime>
 #include <time.h>
 
 #include "webrtc/base/basictypes.h"
@@ -93,6 +94,11 @@ class TimestampWrapAroundHandler {
   int64_t num_wrap_;
 };
 
+// Convert from std::tm, which is relative to 1900-01-01 00:00 to number of
+// seconds from 1970-01-01 00:00 ("epoch").  Don't return time_t since that
+// is still 32 bits on many systems.
+int64_t TmToSeconds(const std::tm& tm);
+
 }  // namespace rtc
 
 #endif  // WEBRTC_BASE_TIMEUTILS_H_