Bug 16181 Tab key doesn't work in editor when 'Insert spaces for tabs' enabled
Using integration build 0515, pressing Tab in an editor window doesn't do anything when 'Insert spaces for tabs' is selected. The editor is marked as unsaved, but no spaces appear.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/CompilationUnitEditor.java
fCachedIsVerticalRulerVisible= (show && fCachedVerticalRuler != null);
			super.showAnnotations(show);
		}
		
		public IContentAssistant getContentAssistant() {
			return fContentAssistant;
		}
		
		/*
		 * @see ITextOperationTarget#doOperation(int)
		 */
		public void doOperation(int operation) {
		
			if (getTextWidget() == null)
				return;
			
			switch (operation) {
				case CONTENTASSIST_PROPOSALS:
					String msg= fContentAssistant.showPossibleCompletions();
					setStatusLineErrorMessage(msg);
					return;
			}
			
			super.doOperation(operation);
		}
		
		public void insertTextConverter(ITextConverter textConverter, int index) {
			throw new UnsupportedOperationException();
		}