Add support for GCM cipher suites from RFC 7714.

webrtc/base/helpers.cc

Index: webrtc/base/helpers.cc
diff --git a/webrtc/base/helpers.cc b/webrtc/base/helpers.cc
index 0a39ee923e1d61b3db9fa6399aee34049595fff6..2612db786483ff5bc5edd146c0aa5ca71b7441e4 100644
--- a/webrtc/base/helpers.cc
+++ b/webrtc/base/helpers.cc
@@ -245,6 +245,10 @@ bool CreateRandomString(size_t len, const std::string& table,
                             static_cast<int>(table.size()), str);
 }
 
+bool CreateRandomData(size_t length, void* data) {
+  return Rng().Generate(data, length);
+}
+
 // Version 4 UUID is of the form:
 // xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx
 // Where 'x' is a hex digit, and 'y' is 8, 9, a or b.