[YouTube] PoToken implementation with HtmlUnit

[Stypox]

What is it?

• Bugfix (user facing)
• Feature (user facing)
• Codebase improvement (dev facing)
• Meta improvement to the project (dev facing)

Description of the changes in your PR

This is an experimental PR that aims to provide an alternative PoTokenProvider implementation that does not rely on the system WebView. HtmlUnit is apparently able to simulate a browser well enough, and the generated poTokens work, however there are a couple of problems:

• The code does not compile unless minSdk is increased to 26 due to this issue. The APK built by this PR has minSdk increased to 26 for testing purposes, but this is obviously not the solution.
• minifyEnabled seems to create issues for release builds.
• While HtmlUnit seems to work without issues in an emulator, on my phone the debug version uses a lot of CPU and after some time the system terminates the app. The release version works fast enough though. Let me know if it works on your phone, try both the debug (from CI) and the release APK (provided below).
• HtmlUnit uses a forked version of Gecko which might conflict with the extractor one.

APK testing

The APK can be found by going to the "Checks" tab below the title. On the left pane, click on "CI", scroll down to "artifacts" and click "app" to download the zip file which contains the debug APK of this PR. You can find more info and a video demonstration on this wiki page.

Release APK built at commit 768db9f with minifyEnabled=false (otherwise it wouldn't build); it might be faster than the debug version: app-release.zip

Due diligence

• I read the contribution guidelines.

[Isira-Seneviratne]

It seems the solution to the build issue is to disable Instant Run.

[gechoto]

What is the benefit of using HtmlUnit compared to the WebView?

[Stypox]

HtmlUnit would be a platform-independent solution that does not rely on the system webview. It could be an alternative for those phones where the WebView implementation is broken or results in invalid poTokens. However, this is mostly an experimental PR, since there are a few problems highlighted above with no clear solution, plus the HtmlUnit library would increase the APK size.

[Isira-Seneviratne]

The system webview is updatable starting with Android 5.0, so this PR might not be necessary.

[Stypox]

That is true in theory, but we all know device manufacturers tend to mess with default Android components more than they should... But yeah this might not be worth it.

[ale5000-git]

The system webview is updatable starting with Android 5.0, so this PR might not be necessary.

The WebView by Google is now Android 8.0+, so other devices are stuck with old WebViews and websites may break on them sooner or later.
There are also other WebViews but the common user would be unable to get them.

[Isira-Seneviratne]

The system webview is updatable starting with Android 5.0, so this PR might not be necessary.

The WebView by Google is now Android 8.0+, so other devices are stuck with old WebViews and websites may break on them sooner or later. There are also other WebViews but the common user would be unable to get them.

In that case, it might be a good idea to bump the app's minimum SDK version to 26.

[ale5000-git]

In that case, it might be a good idea to bump the app's minimum SDK version to 26.

Personally I'm strongly against it, special for this app.
People may keep old phones for music (and YouTube).