Multi-part IME compositions reset cursor in Edge

[Tyriar]

Testing microsoft/vscode#19061

monaco-editor npm version: d38a5e5
Browser: Edge 38.14393.0.0
OS: Windows 10

Related to #320 but the "collapsing" happens when you switch some characters to kanji and start a new string with the Microsoft Japanese IME.

Turn on IME, type "watashi" (わたし):

Press space to confirm 私:

Type "ha" (は), it incorrectly overrides 私:

Pressing enter to confirm the composition results in the correct string:

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This is vscode's behavior:

[rebornix]

IE and Edge are doing differently from Chrome(not v55, v56)/Safari/Firefox about composition update:

In Chrome/Safari/Firefox, type watashi first, you can get composition update of わたし and then if you press ha, and you'll get composition update of わたしは if you don't press enter to confirm わたし.

However in Edge/IE, type watashi first, you can get composition update of わたし and then if you press ha, and you'll get composition update of は **even if** you don't press enter to confirm わたし`.

Here again we have to rely on textarea to get the correct composition input. The fix is clean however it's making our composition logic really complex.

[weinand]

This now works in VSC 1.12.0 on Windows 10 in Edge browser.

[bpasero]

Also seems to be working in Windows 10 VSC standalone.