Bug 170071 [Undo] Undo deleting *.properties file sets explicit encoding
I20070109-1805 Create a *.properties file => Encoding is "Default (determined from content: ISO-8859-1)" Delete file in Navigator, the choose Edit > Undo => File is restored, but its encoding is now explicitly set to "ISO-8859-1"
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/undo/FileDescription.java
*/
	public boolean isValid() {
		if (location != null) {
			return super.isValid();
		}
		return super.isValid() && fileContentDescription != null
				&& fileContentDescription.exists();
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.internal.ide.undo.ResourceDescription#getName()
	 */
	public String getName() {
		return name;
	}
	/*
	 * Get the file state that matches this file description. The local time
	 * stamp is used to try to find a matching file state. If none can be found,
	 * the most recent copy of the file state is used.
	 */
	private IFileState getMatchingFileState(IFileState[] states) {
		for (int i = 0; i < states.length; i++) {
			if (localTimeStamp == states[i].getModificationTime()) {
				return states[i];
			}
		}
		return states[0];
	}
}