Bug 126527 [Field Assist] - API - Field Decoration alignment issues are different for cell editors
bundles/org.eclipse.jface/src/org/eclipse/jface/fieldassist/DecoratedTextCellEditor.java
protected void doSetFocus() {
		if (text != null) {
			
			text.setSelection(text.getText().length());
			
			text.setFocus();
			checkSelection();
			checkDeleteable();
			checkSelectable();
		}
	}
	/**
	 * The <code>TextCellEditor</code> implementation of this
	 * <code>CellEditor</code> framework method accepts a text string (type
	 * <code>String</code>).
	 * 
	 * @param value
	 *            a text string (type <code>String</code>)
	 */
	protected void doSetValue(Object value) {
		Assert.isTrue(text != null && (value instanceof String));
		text.removeModifyListener(getModifyListener());
		text.setText((String) value);
		text.addModifyListener(getModifyListener());
	}
	/**
	 * Processes a modify event that occurred in this text cell editor. This
	 * framework method performs validation and sets the error message
	 * accordingly, and then reports a change via
	 * <code>fireEditorValueChanged</code>. Subclasses should call this