From the application's toolbar at the top of the screen, select the menu icon from the far right hand side. From the list, select "History", then "History" again. On the left hand side of the page that just appeared, select "Clear Browsing Data". At the top of the page that appears, select "Clear browsing data". Select "From the beginning of time" from the drop down menu. Make sure that you check "Browsing history" and "Cached images and files", then click the "Clear browsing data" button.