A Web.config element chrome with an attribute chromeDisableSecurityWarningsBehavior is provided, accepting the values { Automatic, Ignore, Require }.
Automatic
Tries to set the required policy
Throws an UnauthorizedAccessException if write access was denied.
Ignore
"Do nothing", infobar will be shown
Require
Throws an InvalidOperationException if the flag has not been set
As detailed in this PR and these release notes, starting from version 76, all Chromium browsers do not support passing the --disable-infobars command line argument to hide the "Chrome is being controlled by automated test software" message when automating the browser with Selenium.
For Windows versions managed by an organization, the CommandLineFlagSecurityWarningsEnabled enterprise policy options has been added instead to suppress the message (Set Chrome Browser policies on managed PCs).
Adding a DWORD CommandLineFlagSecurityWarningsEnabled with value 0 to the registry path \SOFTWARE\Policies\Google\Chrome should disables the message in Chrome 76 (current developer build) but does nothing on Edge 76, possibly because Chromium Edge does not support policies (yet).
Microsoft Edge v78 (Dev & Canary) supports policies (\SOFTWARE\Policies\Microsoft\Edge)