Partly of #165510

⤴️ Parent PR: #169685 (✅ Merged)
⤴️ Parent PR (refactor): #170618 (✅ Merged)

Re-lands #165531
The PR was originally reverted due to an issue with an internal Google test. I added a new test case under input_decorator_test.dart which does something similar to prevent the regression. All other code is the same as #165531.

The easiest way to review this would probably be to just check the diff after the first commit to see the changes I made. To check if the reland commit is the same, it might be best to just compare solely that commit against the original PR.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• I followed the breaking change policy and added Data Driven Fixes where supported.
• All existing and new tests are passing.

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