webgl memory leak

In easy project, i use www to download a texture. then one cube use texture. after 5sec, i destory this texture. In Unity Profilor, memory release is ok. but In Webgl, memory leak.

how to fix this question?
thanks

If you can confirm that the exact same code has different outcome on different platforms, you should flie a bug report.

https://unity3d.com/unity/qa/bug-reporting