html5 progress bar stays at 0% when archive files are gzipped

[GreenArrow18]

Describe the bug (REQUIRED)
If the files inside the archive folder are gzipped server-side (the arcdX files in particular), the progress bar is shown at 0% and stays there. It does not show any loading progress while the files are being downloaded. From 0%, it goes straight to the fully loaded app.

To Reproduce (REQUIRED)
Steps to reproduce the behavior:

1. Open Chrome developer console
2. Select a 3G network preset to simulate a slow connection
3. Load the app's page
4. After the engine has been loaded, note that the progress bar will be shown with 0% progress
5. Progress bar stays at 0% all the time, then the app is fully loaded. No loading progress is shown at all

Expected behavior (REQUIRED)
Progress bar should show progress from 0% to 100% as the archive files get downloaded.

Defold version (REQUIRED):

• 1.2.172

Platforms (REQUIRED):

• Platforms: HTML5
• OS: Windows 10
• Browser: Google Chrome

Workaround (OPTIONAL):
Do not gzip the files in the archive folder. The progress bar will work as expected, but then you lose the advantage of further reducing download size.

Additional context (OPTIONAL):
File savings when you gzip the archive files are significant (25% or more). For html5 builds, it's very important that the app loads as quickly as possible, so using gzip server-side is almost mandatory. At the same time, the progress bar is also important as it gives the users a visual clue that something is happening in the background.

So we need the progress bar to work when the files in the archive folder have been gzipped.

[d954mas]

Hi cool feature.
It will be better if you move wasm size and percents to constants. So user can configure progress bar.

Thanks.

Use it in my current project. Worked good.

[britzl]

@d954mas I pushed a new commit to the PR. The new commit exposes the values on the EngineLoader object so that you can change them if you use your own engine_template.html

65daeef