Migrate fuzzer to use shiny new metrics2 package

fuzzer/go/generator/afl_generation.go

 package generator
 
 import (
         "fmt"
         "io/ioutil"
         "os"
         "path/filepath"
         "strings"
 
-        go_metrics "github.com/rcrowley/go-metrics"
         "github.com/skia-dev/glog"
         "go.skia.org/infra/fuzzer/go/common"
         "go.skia.org/infra/fuzzer/go/config"
         "go.skia.org/infra/go/exec"
         "go.skia.org/infra/go/fileutil"
         "go.skia.org/infra/go/gs"
+        "go.skia.org/infra/go/metrics2"
         "google.golang.org/cloud/storage"
 )
 
 type Generator struct {
         Category         string
-        fuzzProcessCount go_metrics.Counter
+        fuzzProcessCount *metrics2.Counter
         fuzzProcesses    []exec.Process
 }
 
 func New(category string) *Generator {
         return &Generator{
                 Category:      category,
                 fuzzProcesses: nil,
         }
 }
 
@@ skipping 18 matching lines @@
                 masterCmd.Stdout = os.Stdout
         }
 
         g.fuzzProcesses = append(g.fuzzProcesses, g.run(masterCmd))
 
         fuzzCount := config.Generator.NumFuzzProcesses
         if fuzzCount <= 0 {
                 // TODO(kjlubick): Make this actually an intelligent number based on the number of cores.
                 fuzzCount = 10
         }
-        g.fuzzProcessCount = go_metrics.NewRegisteredCounter("afl_fuzz_process_count", go_metrics.DefaultRegistry)
+        g.fuzzProcessCount = metrics2.NewCounter("afl-fuzz-process-count", map[string]string{"category": g.Category})
         g.fuzzProcessCount.Inc(int64(fuzzCount))
         for i := 1; i < fuzzCount; i++ {
                 fuzzerName := fmt.Sprintf("fuzzer%d", i)
                 slaveCmd := &exec.Command{
                         Name:      "./afl-fuzz",
                         Args:      common.GenerationArgsFor(g.Category, executable, fuzzerName, false),
                         Dir:       config.Generator.AflRoot,
                         LogStdout: true,
                         LogStderr: true,
                         Env:       []string{"AFL_SKIP_CPUFREQ=true"}, // Avoids a warning afl-fuzz spits out about dynamic scaling of cpu frequency
@@ skipping 46 matching lines @@
 // manually kill the command.
 func (g *Generator) run(command *exec.Command) exec.Process {
         p, status, err := exec.RunIndefinitely(command)
         if err != nil {
                 glog.Errorf("Failed afl fuzzer command %#v: %s", command, err)
                 return nil
         }
         go func() {
                 err := <-status
                 g.fuzzProcessCount.Dec(int64(1))
-                glog.Infof(`[%s] afl fuzzer with args %q ended with error "%v".  There are %d fuzzers remaining`, g.Category, command.Args, err, g.fuzzProcessCount.Count())
+                glog.Infof(`[%s] afl fuzzer with args %q ended with error "%v".  There are %d fuzzers remaining`, g.Category, command.Args, err, g.fuzzProcessCount.Get())
         }()
         return p
 }
 
 // Stop terminates all afl-fuzz processes that were spawned,
 // logging any errors.
 func (g *Generator) Stop() {
         glog.Infof("Trying to stop %d fuzz processes", len(g.fuzzProcesses))
         for _, p := range g.fuzzProcesses {
                 if p != nil {
@@ skipping 32 matching lines @@
                         glog.Errorf("[%s] Problem downloading %s from Google Storage, continuing anyway", g.Category, item.Name)
                         return
                 }
                 fileName := filepath.Join(seedPath, strings.SplitAfter(name, gsFolder)[1])
                 if err = ioutil.WriteFile(fileName, content, 0644); err != nil && !os.IsExist(err) {
                         glog.Errorf("[%s] Problem creating binary seed file %s, continuing anyway", g.Category, fileName)
                 }
         })
         return err
 }