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
private int fTabRatio;
		private ILineTracker fLineTracker;
		
		public TabConverter() {
		} 
		
		public void setNumberOfSpacesPerTab(int ratio) {
			fTabRatio= ratio;
		}
		
		public void setLineTracker(ILineTracker lineTracker) {
			fLineTracker= lineTracker;
		}
		
		private int insertTabString(StringBuffer buffer, int offsetInLine) {