skiaserve: Change alpha setting from GET to POST.

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 281 matching lines @@
 };
 
 /**
    Updates the clip visualization alpha. On all subsequent /img requests, the clip will be drawn in
    black with the specified alpha. 0 = no visible clip, 255 = fully opaque clip.
  */
 class ClipAlphaHandler : public UrlHandler {
 public:
     bool canHandle(const char* method, const char* url) override {
         static const char* kBasePath = "/clipAlpha/";
-        return 0 == strcmp(method, MHD_HTTP_METHOD_GET) &&
+        return 0 == strcmp(method, MHD_HTTP_METHOD_POST) &&
                0 == strncmp(url, kBasePath, strlen(kBasePath));
     }
 
     int handle(Request* request, MHD_Connection* connection,
                const char* url, const char* method,
                const char* upload_data, size_t* upload_data_size) override {
         SkTArray<SkString> commands;
         SkStrSplit(url, "/", &commands);
 
         if (!request->fPicture.get() || commands.count() != 2) {
@@ skipping 285 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