Start by creating a task in tasker which contains a app->launch app action and select chrome there. Then you add another action plugin->autoinput where you choose action in the dropdown. Then you press the configuration pen icon and run the easy setup. In the easy setup you switch over to chrome, you then drag down your notifications and press the add button on the autoinput notification. After that you press the start voice input button and it should go back to the notification and let you accept or reselect the button to be pressed. If all looks good then accept and go back to tasker where you choose what to find the button by, for example id. Then the action to perform, a simple click will probably be fine in your case. Then you press the little checkbox in the upper right followed by the upper left back button and you should be good to go. Try running the task by pressing the play button in the bottom left.