Bug 11748 switch to new DecoratorManager API
From the workbench change notes: API changes IWorkbenchPartSite.getDecoratorManager() - As the DecoratorManager has proven to be required for more than just IWorkbenchPartSites we have moved getDecoratorManager() to IWorkbench and deprecated the getDecoratorManager() in IWorkbenchPartSite. The one in IWorkbenchPartSite will be removed after the other Eclipse components have had a chance to switch to the new API.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/browsing/JavaBrowsingPart.java
* Tries to find the given element in a workingcopy.
	 */
	protected static IJavaElement getWorkingCopy(IJavaElement input) {
		try {
			if (input instanceof ICompilationUnit)
				return EditorUtility.getWorkingCopy((ICompilationUnit)input);
			else
				return EditorUtility.getWorkingCopy(input, true);
		} catch (JavaModelException ex) {
		}
		return null;
	}
	/**
	 * Returns the original element from which the specified working copy
	 * element was created from. This is a handle only method, the
	 * returned element may or may not exist.
	 * 
	 * @param	workingCopy the element for which to get the original
	 * @return the original Java element or <code>null</code> if this is not a working copy element
	 */
	protected static IJavaElement getOriginal(IJavaElement workingCopy) {
		ICompilationUnit cu= getCompilationUnit(workingCopy);
		if (cu != null)
			return ((IWorkingCopy)cu).getOriginal(workingCopy);
		return null;
	}
	/**
	 * Returns the compilation unit for the given java element.
	 * 
	 * @param	element the java element whose compilation unit is searched for