Bug 39027 [working sets] Edit active working set prevents removal of closed projects.
When editing the "active working set" closed projects cannot be removed from the working set, the project has to be opened so it can be removed. This is a minor usability issue.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/workingsets/JavaWorkingSetPage.java
Composite composite= new Composite(parent, SWT.NONE);
		composite.setLayout(new GridLayout());
		composite.setLayoutData(new GridData(GridData.HORIZONTAL_ALIGN_FILL));
		setControl(composite);
		Label label= new Label(composite, SWT.WRAP);
		label.setText(WorkingSetMessages.getString("JavaWorkingSetPage.workingSet.name")); 
		GridData gd= new GridData(GridData.GRAB_HORIZONTAL | GridData.HORIZONTAL_ALIGN_FILL | GridData.VERTICAL_ALIGN_CENTER);
		label.setLayoutData(gd);
		fWorkingSetName= new Text(composite, SWT.SINGLE | SWT.BORDER);
		fWorkingSetName.setLayoutData(new GridData(GridData.GRAB_HORIZONTAL | GridData.HORIZONTAL_ALIGN_FILL));
		fWorkingSetName.addModifyListener(
			new ModifyListener() {
				public void modifyText(ModifyEvent e) {
					validateInput();
				}
			}
		);
		fWorkingSetName.setFocus();
		
		label= new Label(composite, SWT.WRAP);
		label.setText(WorkingSetMessages.getString("JavaWorkingSetPage.workingSet.content")); 
		gd= new GridData(GridData.GRAB_HORIZONTAL | GridData.HORIZONTAL_ALIGN_FILL | GridData.VERTICAL_ALIGN_CENTER);
		label.setLayoutData(gd);
		fTree= new CheckboxTreeViewer(composite, SWT.BORDER | SWT.H_SCROLL | SWT.V_SCROLL);
		gd= new GridData(GridData.FILL_BOTH | GridData.GRAB_VERTICAL);
		gd.heightHint= convertHeightInCharsToPixels(15);
		fTree.getControl().setLayoutData(gd);
		
		fTreeContentProvider= new JavaWorkingSetPageContentProvider();
		fTree.setContentProvider(fTreeContentProvider);