skiaserve: Fix /cmd/N and /cmd/N[0|1], the response was never queued.

tools/skiaserve/skiaserve.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrCaps.h"
 #include "GrContextFactory.h"
 #include "SkCanvas.h"
@@ skipping 125 matching lines @@
                                const char* content_type, const char* transfer_encoding,
                                const char* data, uint64_t off, size_t size) {
     struct UploadContext* uc = reinterpret_cast<UploadContext*>(cls);
 
     if (0 != size) {
         uc->fStream.write(data, size);
     }
     return MHD_YES;
 }
 
+// SendOK just sends an empty response with a 200 OK status code.
+static int SendOK(MHD_Connection* connection) {
+    const char* data = "";
+
+    MHD_Response* response = MHD_create_response_from_buffer(strlen(data),
+                                                             (void*)data,
+                                                             MHD_RESPMEM_PERSISTENT);
+    int ret = MHD_queue_response(connection, 200, response);
+    MHD_destroy_response(response);
+    return ret;
+}
+
 static int SendData(MHD_Connection* connection, const SkData* data, const char* type,
                     bool setContentDisposition = false, const char* dispositionString = nullptr) {
     MHD_Response* response = MHD_create_response_from_buffer(data->size(),
                                                              const_cast<void*>(data->data()),
                                                              MHD_RESPMEM_MUST_COPY);
     MHD_add_response_header(response, "Content-Type", type);
 
     if (setContentDisposition) {
         MHD_add_response_header(response, "Content-Disposition", dispositionString);
     }
@@ skipping 65 matching lines @@
         if (commands.count() == 1 && 0 == strcmp(method, MHD_HTTP_METHOD_GET)) {
             int n = request->fDebugCanvas->getSize() - 1;
             return SendJSON(connection, request->fDebugCanvas, n);
         }
 
         // /cmd/N, for now only delete supported
         if (commands.count() == 2 && 0 == strcmp(method, MHD_HTTP_METHOD_DELETE)) {
             int n;
             sscanf(commands[1].c_str(), "%d", &n);
             request->fDebugCanvas->deleteDrawCommandAt(n);
-            return MHD_YES;
+            return SendOK(connection);
         }
 
         // /cmd/N/[0|1]
         if (commands.count() == 3 && 0 == strcmp(method, MHD_HTTP_METHOD_POST))  {
             int n, toggle;
             sscanf(commands[1].c_str(), "%d", &n);
             sscanf(commands[2].c_str(), "%d", &toggle);
             request->fDebugCanvas->toggleCommand(n, toggle);
-            return MHD_YES;
+            return SendOK(connection);
         }
 
         return MHD_NO;
     }
 };
 
 class ImgHandler : public UrlHandler {
 public:
     bool canHandle(const char* method, const char* url) override {
         static const char* kBasePath = "/img";
@@ skipping 295 matching lines @@
     MHD_stop_daemon(daemon);
     return 0;
 }
 
 #if !defined SK_BUILD_FOR_IOS
 int main(int argc, char** argv) {
     SkCommandLineFlags::Parse(argc, argv);
     return skiaserve_main();
 }
 #endif