Add Download.ShowDangerousDownloadConfirmationPrompt for Windows/CrOS
The Download.ShowDangerousDownloadConfirmationPrompt UMA stat tells us
how often people go through the last step of recovering a malicious
binary from chrome://downloads.
This UMA stat was added for GTK, but was missing for Win/CrOS. This CL
adds it to the Views (Win/CrOS) version of the dialog.
BUG=331603
Review URL: https://codereview.chromium.org/
114003005
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243172 0039d316-1c4b-4281-b951-d872f2087c98