Don't enforce the old HMAC key size requirement in FIPS 198 Sec. 3.

crypto/hmac_win.cc

Index: crypto/hmac_win.cc
===================================================================
--- crypto/hmac_win.cc	(revision 125777)
+++ crypto/hmac_win.cc	(working copy)
@@ -104,8 +104,6 @@
   }
 
   if (hash_alg_ == SHA256) {
-    if (key_length < SHA256_LENGTH / 2)
-      return false;  // Key is too short.
     plat_->raw_key_.assign(key, key + key_length);
     return true;
   }