In the generated fiddle, set the portable fonts flag first.

experimental/webtry/webtry.go

 package main
 
 import (
         "bytes"
         "crypto/md5"
         "database/sql"
         "encoding/base64"
         "encoding/binary"
         "encoding/json"
         "flag"
@@ skipping 354 matching lines @@
         return writeTemplate(filename, t, userCode{Code: code, Titlebar: Titlebar{GitHash: gitHash, GitInfo: gitInfo}})
 }
 
 // expandCode expands the template into a file and calculates the MD5 hash.
 func expandCode(code string, source int) (string, error) {
         // in order to support fonts in the chroot jail, we need to make sure
         // we're using portable typefaces.
         // TODO(humper):  Make this more robust, supporting things like setTypeface
 
         inputCodeLines := strings.Split(code, "\n")
-        outputCodeLines := []string{}
+        outputCodeLines := []string{"DECLARE_bool(portableFonts);"}
         for _, line := range inputCodeLines {
                 outputCodeLines = append(outputCodeLines, line)
-                if strings.HasPrefix(strings.TrimSpace(line), "SkPaint ") {
-                        outputCodeLines = append(outputCodeLines, "sk_tool_utils::set_portable_typeface(&p);")
+                if strings.HasPrefix(strings.TrimSpace(line), "SkPaint p") {
+                        outputCodeLines = append(outputCodeLines, "FLAGS_portableFonts = true;")
+                        outputCodeLines = append(outputCodeLines, "sk_tool_utils::set_portable_typeface(&p, \"Helvetica\", SkTypeface::kNormal);")
                 }
         }
 
         fontFriendlyCode := strings.Join(outputCodeLines, "\n")
 
         h := md5.New()
         h.Write([]byte(fontFriendlyCode))
         binary.Write(h, binary.LittleEndian, int64(source))
         hash := fmt.Sprintf("%x", h.Sum(nil))
         // At this point we are running in skia/experimental/webtry, making cache a
@@ skipping 482 matching lines @@
         http.HandleFunc("/sources/", autogzip.HandleFunc(sourcesHandler))
 
         // Resources are served directly
         // TODO add support for caching/etags/gzip
         http.Handle("/res/", autogzip.Handle(http.FileServer(http.Dir("./"))))
 
         // TODO Break out /c/ as it's own handler.
         http.HandleFunc("/", autogzip.HandleFunc(mainHandler))
         log.Fatal(http.ListenAndServe(*port, nil))
 }