Bug 208101 [Markers] Tasks content has mark completed enabled for non editable tasks
I20071030-0100 Mark completed is enabled for tasks that are not editable
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/provisional/views/markers/ExtendedMarkersView.java
* 
		 * @param item
		 * @return boolean <code>true</code> if they are equivalent
		 */
		boolean isEquivalentTo(MarkerItem item) {
			MarkerField[] fields = builder.getGenerator().getVisibleFields();
			if (cachedValues.length != fields.length)
				return false;
			for (int i = 0; i < fields.length; i++) {
				if (cachedValues[i] == fields[i].getValue(item))
					continue;
				return false;
			}
			return true;
		}
	}
	private static int instanceCount = 0;
	private static final String TAG_GENERATOR = "markerContentGenerator"; 
	private static final String TAG_HORIZONTAL_POSITION = "horizontalPosition"; 
	private static final String TAG_VERTICAL_POSITION = "verticalPosition"; 
	private static final String MARKER_FIELD = "MARKER_FIELD"; 
	/**
	 * Return the next secondary id.
	 * 
	 * @return String
	 */
	static String newSecondaryID() {
		return String.valueOf(instanceCount);
	}
	/**