Set ExpectCompute based on the length of the payload

Author: reversefold

src/BizHawk.Client.Common/Api/HttpCommunication.cs

@@ -42,10 +42,14 @@ public string ExecPost(string url = null, string payload = "")
 			).Result;
 		}
 
-		public string ExecPostRaw(string url = null, string payload = "", string contentType = "text/plain") => Post(
-			url ?? PostUrl,
-			new StringContent(payload, Encoding.UTF8, contentType)
-		).Result;
+		public string ExecPostRaw(string url = null, string payload = "", string contentType = "text/plain")
+		{
+			_client.DefaultRequestHeaders.ExpectContinue = payload.Length > ExpectContinueThreshold;
+			return Post(
+				url ?? PostUrl,
+				new StringContent(payload, Encoding.UTF8, contentType)
+			).Result;
+		}
 
 		public async Task<string> Get(string url)
 		{