Update some comments and code to reflect the fact that HMAC() is no longer hostile to NULL key data.

content/child/webcrypto/openssl/hmac_openssl.cc

Index: content/child/webcrypto/openssl/hmac_openssl.cc
diff --git a/content/child/webcrypto/openssl/hmac_openssl.cc b/content/child/webcrypto/openssl/hmac_openssl.cc
index 0872390d457a129fea36030889405ae4dbab9271..c380b37756965f8bbdec724c570f51c593f9fcf6 100644
--- a/content/child/webcrypto/openssl/hmac_openssl.cc
+++ b/content/child/webcrypto/openssl/hmac_openssl.cc
@@ -38,13 +38,9 @@ Status SignHmac(const std::vector<uint8_t>& raw_key,
     return Status::ErrorUnsupported();
   unsigned int hmac_expected_length = EVP_MD_size(digest_algorithm);
 
-  // OpenSSL wierdness here.
-  // First, HMAC() needs a void* for the key data, so make one up front as a
-  // cosmetic to avoid a cast. Second, OpenSSL does not like a NULL key,
-  // which will result if the raw_key vector is empty; an entirely valid
-  // case. Handle this specific case by pointing to a fresh array.
-  const unsigned char null_key[] = {0};
-  const void* const raw_key_voidp = raw_key.size() ? &raw_key[0] : null_key;
+  // HMAC() needs a void* for the key data, so make one up front as a
+  // cosmetic to avoid a cast.
+  const void* const raw_key_voidp = raw_key.empty() ? NULL : &raw_key[0];

[davidben, 2015/03/04 19:40:59]

vector_as_array?

 
   buffer->resize(hmac_expected_length);
   crypto::ScopedOpenSSLSafeSizeBuffer<EVP_MAX_MD_SIZE> hmac_result(