TopComponents created by profiler have non-zero minimum size which prevents the views to be fully minimized.
To reproduce the problem, open a heap dump and drag the IDE main window to decrease its width. At some point the width of HeapWalker stays unchanged according to minimum width of its toolbar.
The problem is more visible in VisualVM where the view is at some point resized back to its preferred size and a scroll bar is added.
Fixed by http://hg.netbeans.org/profiler-main/rev/88a0567789aa.
Integrated into 'main-golden', will be available in build *201211010001* on http://bits.netbeans.org/dev/nightly/ (upload may still be in progress)
User: Jiri Sedlacek <firstname.lastname@example.org>
Log: Bugfix #221044 - profiler top components should have zero minimum size