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
data.visible = true;
		
		
		if (!data.showOnFocus || control.isFocusControl())
			setVisible(data, true);
	}
	/**
	 * Hide the specified decoration. This message has no effect if the
	 * decoration is already hidden, or was not already added to the field using
	 * <code>addFieldDecoration</code>.
	 * 
	 * @param decoration
	 *            the decoration to be hidden.
	 */
	public void hideDecoration(FieldDecoration decoration) {
		FieldDecorationData data = getDecorationData(decoration);
		if (data == null)
			return;
		
		
		
		data.visible = false;
		setVisible(data, false);
	}
	/**
	 * Update the specified decoration. This message should be used if the image
	 * or description in the decoration have changed. This message has no
	 * immediate effect if the decoration is not visible, and no effect at all
	 * if the decoration was not previously added to the field.
	 *