title: How can a Chrome extension respond to a button click in a page?
body: <p>I'm making a first attempt at writing a Chrome extension and I want it to respond to a button click which resembles the facebook like button, G+ button, etc.  This means that I'd like the extension to work on any page, but only respond to a button with a particular ID or something, which seems tricky with the "permission" and/or "matches" item of the JSON manifest.</p>
  
  <p>Since I'm unfamiliar with extensions, should I have the button have its own javascript function which calls/activates the extension somehow, or should I have the extension have an event listener (would this be in a content script?) which listens for a particular button click event?  </p>
  
  <p>Note: I took a look at <a href="https://stackoverflow.com/questions/17723848/chrome-extension-handling-clicks">this question</a>
  but the extension in that case was for a specific web page, so I'm not convinced that the answer will work for me.</p>