Bug 22467 TextEdits: replace != delete + insert
see TextBufferTest.testReplaceAndInsert1
org.eclipse.jdt.ui.tests/ui/org/eclipse/jdt/ui/tests/core/TextBufferTest.java
SwapTextEdit e1= new SwapTextEdit(1, 1, 3, 1);
		SwapTextEdit e2= new SwapTextEdit(5, 1, 7, 1);
		SwapTextEdit e3= new SwapTextEdit(1, 3, 5, 3);
		fEditor.add(e1);
		fEditor.add(e2);
		fEditor.add(e3);
		assertTrue("Can perform edits", fEditor.canPerformEdits());
		UndoMemento undo= fEditor.performEdits(null);
		assertEquals("Buffer content", "0765432189", fBuffer.getContent());
		doUndo(undo);
	}
	public void testSwapAndReplace() throws Exception {
		SwapTextEdit e1= new SwapTextEdit(1, 3, 5, 3);
		SimpleTextEdit e2= SimpleTextEdit.createReplace(6, 1, "ab");
		fEditor.add(e1);
		fEditor.add(e2);
		assertTrue("Can perform edits", fEditor.canPerformEdits());
		UndoMemento undo= fEditor.performEdits(null);
		assertEquals("Buffer content", "05ab7412389", fBuffer.getContent());
		doUndo(undo);
	}
	
	public void testReplaceAndInsert1() throws Exception {
		SimpleTextEdit e1= SimpleTextEdit.createReplace(0, 2, "xx");
		fEditor.add(e1);
		SimpleTextEdit e2= SimpleTextEdit.createInsert(0, "y");
		fEditor.add(e2);	
		assertTrue(fEditor.canPerformEdits());
		UndoMemento undo= fEditor.performEdits(null);
		assertEquals("Buffer content", "xxy23456789", fBuffer.getContent());