Add support for GCM cipher suites from RFC 7714.

webrtc/base/helpers.h

Index: webrtc/base/helpers.h
diff --git a/webrtc/base/helpers.h b/webrtc/base/helpers.h
index 0e7937362a334c7cc29bc9a3ff203c1f7fec647c..c75dba59854184c0e9ed7cfd0d38a631610c3f90 100644
--- a/webrtc/base/helpers.h
+++ b/webrtc/base/helpers.h
@@ -39,6 +39,10 @@ bool CreateRandomString(size_t length, std::string* str);
 bool CreateRandomString(size_t length, const std::string& table,
                         std::string* str);
 
+// Generates (cryptographically) random data of the given length.
+// Return false if the random number generator failed.
+bool CreateRandomData(size_t length, std::string* data);
+
 // Generates a (cryptographically) random UUID version 4 string.
 std::string CreateRandomUuid();