old_contents: chrome.runtime.onInstalled.addListener(function() {
    chrome.declarativeContent.onPageChanged.removeRules(undefined, function() {
      chrome.declarativeContent.onPageChanged.addRules([
        {
          conditions: [
            new chrome.declarativeContent.PageStateMatcher({
              pageUrl: {
                hostEquals: 'github.com',
                schemes: ['https'],
                urlMatches: '/(\\w+)/(\\w+)/issues/(\\d+)'
              },
              css: ['span.js-issue-title', 'span.gh-header-number']
            })
          ],
          actions: [ new chrome.declarativeContent.ShowPageAction() ]
        }
      ]);
    });
  });
  
new_contents: chrome.runtime.onInstalled.addListener(function() {
    chrome.declarativeContent.onPageChanged.removeRules(undefined, function() {
      chrome.declarativeContent.onPageChanged.addRules([
        {
          conditions: [
            new chrome.declarativeContent.PageStateMatcher({
              pageUrl: {
                hostEquals: 'github.com',
                schemes: ['https'],
                urlMatches: '/(.+)/(.+)/issues/(\\d+)'
              },
              css: ['span.js-issue-title', 'span.gh-header-number']
            })
          ],
          actions: [ new chrome.declarativeContent.ShowPageAction() ]
        }
      ]);
    });
  });
  
subject: Fix bug