What unity WebGL does between download and preparation during loading time ?

Hello,

Loading time in webgl is really long (around 30s). WebGL files size are 4.7Mo (for js) + 2.2Mo (for data). I tried to understand why it's so long. I saw logs during custom loading bar: downloading and preparing. But I wanted to know what unity does between these two steps because it takes a long time and I have no idea what's happening. There is a screenshot of chrome's network: http://puu.sh/rzzvV/bd2b20e845.png There is a screenshot of chrome's logs: http://puu.sh/rzzaq/48547c3df8.png

Thanks in advance for any help ;)