Safari/WebKit shouldn't learn input history for input method in private browsing mode

[Makoto Kato]

Windows (Windows 10 20H1+) and Android (API 26+) have IME private mode not to learn input history for input method.
- IS_PRIVATE for Windows (https://docs.microsoft.com/en-us/windows/win32/api/inputscope/ne-inputscope-inputscope)
- IME_FLAG_NO_PERSONALIZED_LEARNING for Android. (https://developer.android.com/reference/android/view/inputmethod/EditorInfo#IME_FLAG_NO_PERSONALIZED_LEARNING)
- GTK_INPUT_HINT_PRIVATE for GTK4. (https://gitlab.gnome.org/GNOME/gtk/-/issues/2261)

So Firefox and Chrome use this flag in private browsing mode, so when using private browsing mode, IME doesn't learn user's input history. But Safari/macOS still learns input history of IME even if private browsing mode.

Safari/macOS shouldn't learn input history of IME even if private browsing mode like Chrome and Firefox. I believe that personal privacy is high priority as Apple, but this issue isn't better than Google, Mozilla and Microsoft.

Reference:
- https://bugs.chromium.org/p/chromium/issues/detail?id=958054
- https://bugzilla.mozilla.org/show_bug.cgi?id=1549394

[Radar WebKit Bug Importer]

<rdar://problem/88554942>

[Alexey Proskuryakov]

Could you please clarify what scenario you are describing? Is this about typing in form controls on the page, or into Safari controls like the address bar, or tab names or anything like that?

[Brent Fulgham]

Note that the bug reported here requires changes outside of the WebKit project. Consequently, this bug is being flagged as "RESOLVED | MOVED".