Bug 19075 Rename Java file to non Java file causes most actions to crash
F2 - open Java file in editor - rename it so that it has the extension .txt Almost all Java relevant actions in Edit, Source, Refactor, Naviagte and context menu are still enabled. Executing them almost always leads to some sort of exceptions.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/CompilationUnitEditor.java
*/
		public void setDocument(IDocument document, IAnnotationModel annotationModel, int visibleRegionOffset, int visibleRegionLength) {
			super.setDocument(document, annotationModel, visibleRegionOffset, visibleRegionLength);
			fOverviewRuler.setModel(annotationModel);
		}
		
		
		public void updateIndentationPrefixes() {
			SourceViewerConfiguration configuration= getSourceViewerConfiguration();
			String[] types= configuration.getConfiguredContentTypes(this);
			for (int i= 0; i < types.length; i++) {
				String[] prefixes= configuration.getIndentPrefixes(this, types[i]);
				if (prefixes != null && prefixes.length > 0)
					setIndentPrefixes(prefixes, types[i]);
			}
		}
		
		/*
		 * @see IWidgetTokenOwner#requestWidgetToken(IWidgetTokenKeeper)
		 */
		public boolean requestWidgetToken(IWidgetTokenKeeper requester) {
			
			IHelp help= WorkbenchHelp.getHelpSupport();
			if (help != null && help.isContextHelpDisplayed())
				return false;
			return super.requestWidgetToken(requester);
		}
	};
	
	static class TabConverter implements ITextConverter {