Update ecmascript_simd.js to 841990cfbd63188b4d9931b540a383b90e1388a5

Update the SIMD API in mandelbrot.js accordingly.
Merge pull request #1 from huningxin/update_ecmascript_simd

Update ecmascript_simd.js to 841990cfbd63188b4d9931b540a383b90e1388a5