Issue 127. canvas_perf updation.

Hi Bryce,
In flashcanvas JS, var value = counter / (now - start_time) is being used.
i. The counter value is incremented for each context execution, so ideally it should be iterations*context_size.
ii. Time value they use is total time taken for execution where we were using time taken for one iteration.
iii. They choose no of iteration based on some timeout method it seems. As of now i am using 100 as iteration value.
Changes are tested in device and PC. Kindly review the same. 

Thanks,
Suyambu