Based on issue #144903, this PR aims to bring the codebase more in line with the [Flutter repo style guide](https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#avoid-using-if-chains-or--or--with-enum-values):

> #### Avoid using `if` chains or `?:` or `==` with enum values

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This change unfortunately increases the total line length, but it also improves readability.