Benchmark rates the performance of the device based on how long it
takes the app to add 5000 empty entities to the stage.  The higher the
number the better the performance.

Call Benchmark.start(functionName). functionName will be called when
the test is complete.  You can also call Benchmark.results() to get the
value

From my own tests
- low performance: under 2000
- high performance: above 2000

cleaning code

Adding 5000 entites to the stage caused a maximum call stack error in
html release build.  Benchmark now adds 5000 empty pointer disabled
sprites to one entity added to the stage.