Add WARN_UNUSED_RESULT to crypto/hmac.h

net/http/http_mac_signature.h

Index: net/http/http_mac_signature.h
diff --git a/net/http/http_mac_signature.h b/net/http/http_mac_signature.h
index 00191e1aec362ad607df3cdb12416216a3e16dd7..7a1e9719585e1b57a762b0bebdb2afc799d1aec5 100644
--- a/net/http/http_mac_signature.h
+++ b/net/http/http_mac_signature.h
@@ -39,20 +39,24 @@ class NET_TEST HttpMacSignature {
                    const std::string& host,
                    int port);
 
-  // Returns the value of the Authorization header for use in an HTTP request.
-  std::string GenerateAuthorizationHeader();
+  // Generates the Authorization header for use in an HTTP request. If
+  // successfully generated, returns true and stores the resultant header in
+  // |*header|.
+  bool GenerateAuthorizationHeader(std::string* header);
 
  private:
   FRIEND_TEST_ALL_PREFIXES(HttpMacSignatureTest, GenerateHeaderString);
   FRIEND_TEST_ALL_PREFIXES(HttpMacSignatureTest, GenerateNormalizedRequest);
   FRIEND_TEST_ALL_PREFIXES(HttpMacSignatureTest, GenerateMAC);
 
-  std::string GenerateHeaderString(const std::string& age,
-                                   const std::string& nonce);
+  bool GenerateHeaderString(const std::string& age,
+                            const std::string& nonce,
+                            std::string* header);
   std::string GenerateNormalizedRequest(const std::string& age,
                                         const std::string& nonce);
-  std::string GenerateMAC(const std::string& age,
-                          const std::string& nonce);
+  bool GenerateMAC(const std::string& age,
+                   const std::string& nonce,
+                   std::string* mac);
 
   std::string id_;
   base::Time creation_date_;