(Googlers only) Generally, the histogram or action data is available in the Timeline category of the UMA page.
DevTools.ActionTaken.DevTools.ActionTaken is a generic histogram for tracking actions performed via the DevTools front-end.DevTools.PanelShown counts how often a given panel or tab is shown in the DevTools front-end.DevTools.ActionTaken records AddFileSystemToWorkspace (Add Filesystem to Workspace), RemoveFileSystemFromWorkspace (Remove Filesystem from Workspace) and FileSystemSourceSelected (Filesystem source selected) according to developer interactions with the Filesystem tab in the Sources panels sidebar.DevTools.Workspaces.PopulateWallClockTime records the wall clock time in milliseconds elapsed while populating a project folder in the workspace.DevTools.SidebarPaneShown records the navigator-files (Sources - Filesystem) enum whenever the Filesystem tab is revealed in the Sources panels sidebar.