Enable Developer Dashboard using Powershell

$spDevDash = [Microsoft.SharePoint.Administration.SPWebService]::ContentService.DeveloperDashboardSettings;
$spDevDash .DisplayLevel = [Microsoft.SharePoint.Administration.SPDeveloperDashboardLevel]::OnDemand;
$spDevDash .RequiredPermissions = ‘EmptyMask’;
$spDevDash .TraceEnabled = $true;
$spDevDash .Update();

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