On WebGL build, SetProgress function is not called when decompressing compressed files in Release directory. Instead, SetProgress gets called many times after decompression is done.

Reproduction steps:
1. Create new project
2. Set WebGL template as "default" in player settings
3. Build project as WebGL build
4. Run the index.html file

Expected result: loading bar moves smoothly from start to end
Actual result: loading bar jumps only once while loading.

This happens because SetProgress is called once before files decompression and many times on the same frame after decompression.

Tested on: Unity 5.4.1f1, 5.3.3f1.