title: chrome.runtime.sendMessage throws exception from content script after reloading Chrome Extension
body: <p>I send messages from the injected <em>content scripts</em> back to my <em>background script</em> in my Chrome Extension as such:</p>
  
  <pre><code>chrome.runtime.sendMessage({action: "myResult"});
  </code></pre>
  
  <p>This works fine, until I reload my extension (by going to Settings -> Extensions -> "Reload (Ctrl+R)" for my extension.)</p>
  
  <p>In turn when my <em>background script</em> starts up it repeatedly calls <code>chrome.tabs.executeScript</code> for all open tabs to programmatically re-inject my <em>content script</em> (<a href="https://stackoverflow.com/q/25839819/843732">as I showed in this question</a>.)</p>
  
  <p>But after I do that, if I call that first <code>sendMessage</code> line from my <em>content script</em>, it throws this exception:</p>
  
  <blockquote>
    <p>Error: Error connecting to extension my_extension_id</p>
  </blockquote>
  
  <p>Any idea why this happens?</p>