old_contents: chrome.app.runtime.onLaunched.addListener(function() {
      chrome.app.window.create('html/beagle.html', {
          width: 1024,
          height: 768
      }, function(win) {
          win.onClosed.addListener(function() {
              console.log("called at onClosed");
              serial_lib.closeSerial(function() {
                  console.log("close successfully");
              });
          });
      });
  })
  
new_contents: chrome.app.runtime.onLaunched.addListener(function() {
      chrome.app.window.create('html/beagle.html', {
          'bounds': {
              width: 1024,
              height: 768
          }
      }, function(win) {
          win.onClosed.addListener(function() {
              console.log("called at onClosed");
              serial_lib.closeSerial(function() {
                  console.log("close successfully");
              });
          });
      });
  })
  
subject: Use bounds property to set window size