Bug 124202 [Field Assist] - decorated fields should not size the created control
The philosophy of DecoratedField is that the client creates the target control and accesses it with normal SWT coding. The decorated field manages the decorations but otherwise statys out of the way. This philosophy is violated when DecoratedField sets the width of the field to IDialogConstants.ENTRY_WIDTH. Sizing decisions should be made by the client of the decorated field, not the field itself.
bundles/org.eclipse.jface/src/org/eclipse/jface/fieldassist/DecoratedField.java
* This value is used as the minimum width for any decorations that have
	 * been added to the field, and can be used by clients to compute margins in
	 * order to align non-decorated fields with decorated fields.
	 * 
	 * @return decorationWidth the width in pixels reserved for decorations
	 */
	public static int getReservedDecorationWidth() {
		return RESERVED_WIDTH;
	}
	/**
	 * Set the width (in pixels) that should always be reserved for field
	 * decorations, regardless of the actual width of any supplied decorations.
	 * Field alignment within dialogs will look best when all decorations
	 * supplied conform to the reserved width. However, the field decoration
	 * area for a particular field will be expanded if decorations larger than
	 * the reserved width are supplied.
	 * 
	 * @param decorationWidth
	 *            the width in pixels reserved for decorations
	 */
	public static void setReservedDecorationWidth(int decorationWidth) {
		RESERVED_WIDTH = decorationWidth;
	}
	/**
	 * Simple data structure class for specifying the internals for a field
	 * decoration. This class contains data specific to the implementation of
	 * field decorations as labels attached to the field. Clients should use
	 * <code>FieldDecoration</code> for specifying a decoration.
	 */
	private class FieldDecorationData {