Source Tree's custom form doesn't open the system menu (also called Window Menu) on left clicking the icon.

Please note: This issue relates to other issues because of the custom form implementation of source tree.
- is related to
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                    SRCTREEWIN-7854 Aero Snap is not fully supported -         
- Needs Triage
 
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- relates to
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                    SRCTREEWIN-7680 Can't resize window from the top -         
- Closed
 
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                    SRCTREEWIN-7852 No Top Corner Resizing -         
- Closed
 
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                    SRCTREEWIN-7381 Can't resize window using the top edge. -         
- Closed
 
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