Bug 91899 [Markers] IMarker.setAttribute fails when attributeName = IMarker.LOCATION
Calling setAttribute(IMarker.LOCATION, "foo") on an IMarker instance does nothing---the "Location" column in the Problem View remains blank.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/views/markers/internal/ConcreteMarker.java
* Clears any cached information. This frees up some memory, but will slow down
     * the next comparison operation. It is a good idea to call this on a set of markers
     * after sorting them, in order to reduce their memory cost. 
     */
    public void clearCache() {
        resourceNameKey = null;
        descriptionKey = null;
    }
    /**
     * Refresh the properties of this marker from the underlying IMarker instance
     */
    public void refresh() {
        clearCache();
        description = Util.getProperty(IMarker.MESSAGE, marker);
        resourceName = Util.getResourceName(marker);
        inFolder = Util.getContainerName(marker);
        shortFolder = null;
        line = marker.getAttribute(IMarker.LINE_NUMBER, -1);
        try {
            creationTime = marker.getCreationTime();
        } catch (CoreException e) {
            creationTime = 0;
        }
        try {
            type = marker.getType();
        } catch (CoreException e1) {
            type = Util.EMPTY_STRING; 
        }