WIP: [windows] Add PlatformView support for Win32

[eggfly]

Implements:

• https://github.com/flutter/flutter/issues/31713

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[flutter-dashboard[bot]]

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption to this rule, contact Hixie on the #hackers channel in Chat (don't just cc him here, he won't see it! He's on Discord!).

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[flutter-dashboard[bot]]

This pull request executed golden file tests, but it has not been updated in a while (20+ days). Test results from Gold expire after as many days, so this pull request will need to be updated with a fresh commit in order to get results from Gold.

[wanjm]

any one take care of this?

[wanjm]

or any plan for platformview in flutter, it seems it last a long time

[cbracken]

Since this patch has been WIP with no changes since April, and doesn't look ready for review (lots of commented out code/debug logging) I'm going to close this for now. If you do have a more recent/complete implementation please open a new PR and add reviewers when ready.

For others inquiring about PlatformView support on desktop. PlatformView support for the macOS embedder is getting close, Windows support is something that @loic-sharma will be working on soon.