Check that table evenly divides 256 when generating random string.

webrtc/base/helpers.h

Index: webrtc/base/helpers.h
diff --git a/webrtc/base/helpers.h b/webrtc/base/helpers.h
index 0e7937362a334c7cc29bc9a3ff203c1f7fec647c..c7cb65e17be4a27249aaa76d40aaa005e5f41a8b 100644
--- a/webrtc/base/helpers.h
+++ b/webrtc/base/helpers.h
@@ -35,7 +35,7 @@ bool CreateRandomString(size_t length, std::string* str);
 
 // Generates a (cryptographically) random string of the given length,
 // with characters from the given table. Return false if the random
-// number generator failed.
+// number generator failed or the table doesn't evenly divide 256.

[mattdr-at-webrtc.org, 2016/07/01 22:34:22]

number generator failed. For ease of implementation, the function requires that
the table size evenly divide 256; otherwise, it returns false.

[joachim, 2016/07/01 22:37:10]

Done.

 bool CreateRandomString(size_t length, const std::string& table,
                         std::string* str);