Add a basic performance benchmark test for DevTools.

[kenzieschmoll]

This benchmark yields measurements like:

  "devtools_navigateThroughOfflineScreens": [
    {
      "metric": "preroll_frame.average",
      "value": 63.88095238095238
    },
    {
      "metric": "preroll_frame.outlierAverage",
      "value": 204.71428571428572
    },
    {
      "metric": "preroll_frame.outlierRatio",
      "value": 3.204621692135669
    },
    {
      "metric": "preroll_frame.noise",
      "value": 0.7518520780580912
    },
    {
      "metric": "apply_frame.average",
      "value": 113.95094339622642
    },
    {
      "metric": "apply_frame.outlierAverage",
      "value": 787.375
    },
    {
      "metric": "apply_frame.outlierRatio",
      "value": 6.909771666059542
    },
    {
      "metric": "apply_frame.noise",
      "value": 0.5800946479746519
    },
    {
      "metric": "drawFrameDuration.average",
      "value": 2140.381679389313
    },
    {
      "metric": "drawFrameDuration.outlierAverage",
      "value": 24381.727272727272
    },
    {
      "metric": "drawFrameDuration.outlierRatio",
      "value": 11.391298807829354
    },
    {
      "metric": "drawFrameDuration.noise",
      "value": 0.3521587258527538
    },
    {
      "metric": "totalUiFrame.average",
      "value": 4958
    }
  ],

Work towards #6552