[webcrypto] Refactor some of the algorithm parameter names.

Source/modules/crypto/HmacKeyParams.cpp

Index: Source/modules/crypto/HmacKeyParams.cpp
diff --git a/Source/modules/crypto/HmacKeyParams.cpp b/Source/modules/crypto/HmacKeyParams.cpp
index 2d2c5bbc453c53a5ce41c506f10a9b403b3cf12b..1db7e15e526d09e35ef22d101464c6d246651148 100644
--- a/Source/modules/crypto/HmacKeyParams.cpp
+++ b/Source/modules/crypto/HmacKeyParams.cpp
@@ -44,9 +44,8 @@ Algorithm* HmacKeyParams::hash()
 
 unsigned HmacKeyParams::length(bool& isNull)
 {
-    unsigned length = 0;
-    isNull = !m_algorithm.hmacKeyParams()->getLength(length);
-    return length;
+    isNull = !m_algorithm.hmacKeyParams()->hasLengthBytes();
+    return m_algorithm.hmacKeyParams()->optionalLengthBytes();
 }
 
 HmacKeyParams::HmacKeyParams(const blink::WebCryptoAlgorithm& algorithm)