[webcrypto] Add the KeyAlgorithm interface.

Source/modules/crypto/HmacKeyAlgorithm.h

Index: Source/modules/crypto/HmacKeyAlgorithm.h
diff --git a/Source/platform/fonts/FontCacheClient.h b/Source/modules/crypto/HmacKeyAlgorithm.h
similarity index 79%
copy from Source/platform/fonts/FontCacheClient.h
copy to Source/modules/crypto/HmacKeyAlgorithm.h
index 4e43b8c72cf93e9d6f51f68098d434a9d97444ce..800e52ce4e1afceedea4bf68a93e6cf2ec90515a 100644
--- a/Source/platform/fonts/FontCacheClient.h
+++ b/Source/modules/crypto/HmacKeyAlgorithm.h
@@ -28,21 +28,27 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef FontCacheClient_h
-#define FontCacheClient_h
+#ifndef HmacKeyAlgorithm_h
+#define HmacKeyAlgorithm_h
 
-#include "platform/PlatformExport.h"
-#include "wtf/RefCounted.h"
+#include "modules/crypto/KeyAlgorithm.h"
 
 namespace WebCore {
 
-class PLATFORM_EXPORT FontCacheClient : public RefCounted<FontCacheClient> {
+class HmacKeyAlgorithm : public KeyAlgorithm {
 public:
-    virtual ~FontCacheClient() { }
+    static PassRefPtrWillBeRawPtr<HmacKeyAlgorithm> create(const blink::WebCryptoKeyAlgorithm&);
 
-    virtual void fontCacheInvalidated() = 0;
+    KeyAlgorithm* hash();
+
+    void trace(Visitor*);
+
+protected:
+    explicit HmacKeyAlgorithm(const blink::WebCryptoKeyAlgorithm&);
+
+    RefPtrWillBeMember<KeyAlgorithm> m_hash;
 };
 
 } // namespace WebCore
 
-#endif // FontCacheClient_h
+#endif