Fix ToolStrip memory leak due to MouseHoverTimer and #4808

[kirsan31]

Fix #4808 and problem that was mentioned in #11334.

Proposed changes

Replace ToolStripItem? _currentItem with WeakReference<ToolStripItem?> _currentItem in MouseHoverTimer
Implement this suggestion.

Customer Impact

No more memory leak if ToolStripItem will be disposed after MouseHoverTimer start.
No more memory leak of chilled elements due to DisplayedItems and OverflowItems collections..

Regression?

• No

Risk

Minimal.

Screenshots

ToolStripItem below was disposed, but remain in memory:

Test methodology

• Existing unit tests.
• New unit tests.
• Manual with test app from ToolStripMenuItem can lead to memory leaks #4808.

Microsoft Reviewers: Open in CodeFlow

[codecov]

Codecov Report

Attention: Patch coverage is 98.57143% with 1 line in your changes missing coverage. Please review.

Project coverage is 75.26360%. Comparing base (6b443fc) to head (ccc87f9).

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #11358         +/-   ##
===================================================
+ Coverage   75.25676%   75.26360%   +0.00683%     
===================================================
  Files           3085        3085                 
  Lines         633571      633629         +58     
  Branches       46831       46839          +8     
===================================================
+ Hits          476805      476892         +87     
+ Misses        153368      153337         -31     
- Partials        3398        3400          +2     

Flag	Coverage Δ
Debug	75.26360% <98.57143%> (+0.00683%)	⬆️
integration	18.02555% <90.00000%> (+0.01323%)	⬆️
production	48.56822% <95.00000%> (+0.01163%)	⬆️
test	97.02282% <100.00000%> (+0.00041%)	⬆️
unit	45.57567% <95.00000%> (+0.02543%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

[kirsan31]

Added commit that fix #4808 (thanks to @elachlan).

[elachlan]

@Olina-Zhang Could your team please test this pr to confirm the issues are resolved?

[Olina-Zhang]

@Olina-Zhang Could your team please test this pr to confirm the issues are resolved?

@elachlan @kirsan31 Tested this PR, just can confirm that GH issue #4808 is fixed, I am not clear how to verify #11334, can you give some more information about how to repro it?

• GH issue ToolStripMenuItem can lead to memory leaks #4808 validation
  

[kirsan31]

@Olina-Zhang

can you give some more information about how to repro it?

Same repro app, the key is to remove item immediately after MouseHoverTimer has started. So simply hover and immediately click:

timer.mp4

[Olina-Zhang]

@kirsan31 thanks for your info.
Adding the GH issue #11334 validation: fixed