Verifies that Overlay.setShowViewportSizeOnResize works.
Response to setDeviceMetricsOverride:
{
    id : <number>
    result : {
    }
    sessionId : <string>
}
Initial device metrics:
[
  {
    "name": "reset",
    "data": {
      "deviceScaleFactor": 1,
      "emulationScaleFactor": 1,
      "pageScaleFactor": 1,
      "viewportSize": {
        "width": 800,
        "height": 600
      },
      "viewportSizeForMediaQueries": {
        "width": 800,
        "height": 600
      },
      "pageZoomFactor": 1,
      "scrollX": 0,
      "scrollY": 0
    }
  }
]
Response to setDeviceMetricsOverride:
{
    id : <number>
    result : {
    }
    sessionId : <string>
}
Device metrics with changed viewport:
[
  {
    "name": "setOverlay",
    "data": "viewportSize"
  },
  {
    "name": "reset",
    "data": {
      "deviceScaleFactor": 1,
      "emulationScaleFactor": 1,
      "pageScaleFactor": 1,
      "viewportSize": {
        "width": 500,
        "height": 500
      },
      "viewportSizeForMediaQueries": {
        "width": 500,
        "height": 500
      },
      "pageZoomFactor": 1,
      "scrollX": 0,
      "scrollY": 0
    }
  },
  {
    "name": "drawViewSize",
    "data": ""
  }
]
Response to setDeviceMetricsOverride:
{
    id : <number>
    result : {
    }
    sessionId : <string>
}
Device metrics with scrollbar:
[
  {
    "name": "setOverlay",
    "data": "viewportSize"
  },
  {
    "name": "reset",
    "data": {
      "deviceScaleFactor": 1,
      "emulationScaleFactor": 1,
      "pageScaleFactor": 1,
      "viewportSize": {
        "width": 300,
        "height": 300
      },
      "viewportSizeForMediaQueries": {
        "width": 300,
        "height": 300
      },
      "pageZoomFactor": 1,
      "scrollX": 0,
      "scrollY": 0
    }
  },
  {
    "name": "drawViewSize",
    "data": ""
  }
]