Use size_t as the type of key_length and digest_length arguments of HMAC.

crypto/hmac_openssl.cc

Index: crypto/hmac_openssl.cc
===================================================================
--- crypto/hmac_openssl.cc	(revision 170598)
+++ crypto/hmac_openssl.cc	(working copy)
@@ -26,7 +26,7 @@
   DCHECK(hash_alg_ == SHA1 || hash_alg_ == SHA256);
 }
 
-bool HMAC::Init(const unsigned char* key, int key_length) {
+bool HMAC::Init(const unsigned char* key, size_t key_length) {
   // Init must not be called more than once on the same HMAC object.
   DCHECK(plat_->key.empty());
 
@@ -42,8 +42,7 @@
 
 bool HMAC::Sign(const base::StringPiece& data,
                 unsigned char* digest,
-                int digest_length) const {
-  DCHECK_GE(digest_length, 0);
+                size_t digest_length) const {
   DCHECK(!plat_->key.empty());  // Init must be called before Sign.
 
   ScopedOpenSSLSafeSizeBuffer<EVP_MAX_MD_SIZE> result(digest, digest_length);