Bug 28698 Ctrl+O (show outline) does not work if the file being shown in the editor is read only
M4 The summary tells all. Works if the file is not read only. Is this by design?
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/CompilationUnitEditor.java
fBracketInserter.setCloseBracketsEnabled(closeBrackets);
		fBracketInserter.setCloseStringsEnabled(closeStrings);
		
		ISourceViewer sourceViewer= getSourceViewer();
		if (sourceViewer instanceof ITextViewerExtension)
			((ITextViewerExtension) sourceViewer).prependVerifyKeyListener(fBracketInserter);
	}
	
	private static char getPeerCharacter(char character) {
		switch (character) {
			case '(':
				return ')';
				
			case ')':
				return '(';
				
			case '[':
				return ']';
			case ']':
				return '[';
				
			case '"':
				return character;
			
			default:
				throw new IllegalArgumentException();
		}					
	}
	
	private static class ExitPolicy implements LinkedPositionUI.ExitPolicy {