These action chains are invalid for later versions of selenium (which
are needed for upgrading the version of firefox we test on); they will
result in output like this:

```
 WebDriverException: Message: UnknownError: Cannot release a button when no button is pressed.'UnknownError: Cannot release a button when no button is pressed.' when calling method: [wdIMouse::up]
   Stacktrace:
       at FirefoxDriver.prototype.mouseButtonUp (file:///tmp/tmp6LL1Ye/extensions/fxdriver@googlecode.com/components/driver-component.js:10979)
       at DelayedCommand.prototype.executeInternal_/h (file:///tmp/tmp6LL1Ye/extensions/fxdriver@googlecode.com/components/command-processor.js:12534)
       at DelayedCommand.prototype.executeInternal_ (file:///tmp/tmp6LL1Ye/extensions/fxdriver@googlecode.com/components/command-processor.js:12539)
       at DelayedCommand.prototype.execute/< (file:///tmp/tmp6LL1Ye/extensions/fxdriver@googlecode.com/components/command-processor.js:12481)

```