base::MD5Clone() clones MD5Context.

base/md5.h

Index: base/md5.h
diff --git a/base/md5.h b/base/md5.h
index fba02bd11635d63ac2057e25cf150bc25d84f012..31c1fac18f5e227ec63168bd1ee7af94de09d8dc 100644
--- a/base/md5.h
+++ b/base/md5.h
@@ -55,6 +55,12 @@ BASE_EXPORT void MD5Init(MD5Context* context);
 // during the computation, except that MD5Init() must have been called first.
 BASE_EXPORT void MD5Update(MD5Context* context, const StringPiece& data);
 
+// Clone |original_context| into |clone_context|.  MD5Final() modifies the
+// context when generating the digest.  MD5Clone() can be used to generate a
+// digest from a copy of the context.
+BASE_EXPORT void MD5Clone(MD5Context* clone_context,
+                          MD5Context* original_context);
+
 // Finalizes the MD5 operation and fills the buffer with the digest.
 BASE_EXPORT void MD5Final(MD5Digest* digest, MD5Context* context);