fix: prevent erroneous new main frame

[adamraine]

For reasons I am still investigating, Chrome will sometimes emit a random Page.frameNavigated event that looks like this:

{
  "id": "FC1767E7420AFDD8D5D7CD935DA4C788",
  "loaderId": "E4B73E277690F2C9755A2D0C950D2FA0",
  "url": ":",
  "domainAndRegistry": "",
  "securityOrigin": "://",
  "mimeType": "text/html",
  "adFrameStatus": {
    "adFrameType": "none"
  },
  "secureContextType": "InsecureScheme",
  "crossOriginIsolatedContextType": "NotIsolatedFeatureDisabled",
  "gatedAPIFeatures": []
}

The frame ID of this event is not the same frame id as the actual main frame of the tree, however it is set as the main frame since it doesn't have a parent id.

It happens when running Lighthouse in DevTools:
GoogleChrome/lighthouse#15073

This patch ensures that the main frame of a frame tree can only be set one time so this random event does not influence the frame tree.

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[adamraine]

@OrKoN are the CI failures related to this patch?

[OrKoN]

@adamraine did you find a reason why this event is emitted?

[adamraine]

Not yet, planning on doing more investigation today.

[OrKoN]

@OrKoN are the CI failures related to this patch?

probably not, restarted the failing check.

[adamraine]

Update on investigation, this appears to be coming from a fenced frame (notice the target subtype). Still not sure exactly how this event gets created though.

{
  "method": "Target.attachedToTarget",
  "params": {
    "sessionId": "221795A5659470D7AC6FCBF3F311D882",
    "targetInfo": {
      "targetId": "F5B7345C9BF9413F71A9B51D22304A82",
      "type": "iframe",
      "title": "",
      "url": "",
      "attached": true,
      "canAccessOpener": false,
      "browserContextId": "6310EBC13B0F02CB468081EC10C1A4B0",
      "subtype": "fenced"
    },
    "waitingForDebugger": true
  },
  "sessionId": "B5668ED04C68E8A4178A04D5EE1EB6E0"
}

Frame tree:

{
  "frame": {
    "id": "F5B7345C9BF9413F71A9B51D22304A82",
    "loaderId": "4BDF72DDE41DDD533EFDE652EB563B30",
    "url": ":",
    "domainAndRegistry": "",
    "securityOrigin": "://",
    "mimeType": "text/html",
    "adFrameStatus": {
      "adFrameType": "none"
    },
    "secureContextType": "InsecureScheme",
    "crossOriginIsolatedContextType": "NotIsolatedFeatureDisabled",
    "gatedAPIFeatures": []
  }
}

[OrKoN]

@adamraine I believe the event might be created in the same place as for regular frames. The problem seems to be that the fenced frame does not report a parent id. It is probably because it is 'fenced' but for CDP purposes we might need to still report it. Would you mind filing a crbug so that we can discuss? cc @caseq

[adamraine]

https://bugs.chromium.org/p/chromium/issues/detail?id=1464949