…er text input (flutter/engine#46032)

…135744)

flutter/engine@09130bf...8b4e633

2023-09-29 [email protected] [macOS] Ensure first responder is consistent during and after text input (flutter/engine#46032)

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…lutter#135744)

flutter/engine@09130bf...8b4e633

2023-09-29 [email protected] [macOS] Ensure first responder is consistent during and after text input (flutter/engine#46032)

If this roll has caused a breakage, revert this CL and stop the roller
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…put (#46032)

Fixes flutter/flutter#134906
Fixes flutter/flutter#133832

This ensures that there are only two first responder widgets -
`FlutterView` when text input is not active and `TextInputPlugin` when
text input is active. The PR also prevents `FlutterView` stealing first
responder status on mouse click events during text input.

Previously when `TextInputClient` resigned it made `nextResponder` the
first responder, but that was incorrect - `nextResponder` being the
superview (`FlutterViewWrapper`).

## Pre-launch Checklist

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- [X] I read and followed the [Flutter Style Guide] and the [C++,
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- [X] I listed at least one issue that this PR fixes in the description
above.
- [X] I added new tests to check the change I am making or feature I am
adding, or the PR is [test-exempt]. See [testing the engine] for
instructions on writing and running engine tests.
- [X] I updated/added relevant documentation (doc comments with `///`).
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- [X] All existing and new tests are passing.

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