base: Remove using declaration of MD5Digest now that hunspell was fixed.

net/socket/web_socket_server_socket.cc

Index: net/socket/web_socket_server_socket.cc
diff --git a/net/socket/web_socket_server_socket.cc b/net/socket/web_socket_server_socket.cc
index a793097cbc70a66b21dd322c6e9998070eec824c..7b17ae739dca0d37b075630a960290aff6a87483 100644
--- a/net/socket/web_socket_server_socket.cc
+++ b/net/socket/web_socket_server_socket.cc
@@ -699,8 +699,8 @@ class WebSocketServerSocketImpl : public net::WebSocketServerSocket {
     memcpy(challenge, &part1, 4);
     memcpy(challenge + 4, &part2, 4);
     memcpy(challenge + 4 + 4, key3, sizeof(key3));
-    MD5Digest challenge_response;
-    MD5Sum(challenge, sizeof(challenge), &challenge_response);
+    base::MD5Digest challenge_response;
+    base::MD5Sum(challenge, sizeof(challenge), &challenge_response);
 
     // Concocting response handshake.
     class Buffer {