Prevent placeholder from appearing on inputs with focus
Prevent placeholder from appearing on inputs with focus

An angular bug with the tab key causes $render to be triggered late,
after the next input is already focused. Add a check to prevent
setValue() from adding placeholder text to the focused input. Also
add some comments.

cvn/angular-shims-placeholder,radotzki/angular-shims-placeholder,cvn/angular-shims-placeholder,akkunchoi/angular-shims-placeholder,akkunchoi/angular-shims-placeholder,radotzki/angular-shims-placeholder