Bug 68011 [java search] "Search the JRE System Libraries" looks like a local preference but behaves as a global one... [search]
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/search/JavaSearchPage.java
private SearchPatternData findInPrevious(String pattern) {
		for (Iterator iter= fPreviousSearchPatterns.iterator(); iter.hasNext();) {
			SearchPatternData element= (SearchPatternData) iter.next();
			if (pattern.equals(element.getPattern())) {
				return element;
			}
		}
		return null;
	}
	
	/**
	 * Return search pattern data and update previous searches.
	 * An existing entry will be updated.
	 */
	private SearchPatternData getPatternData() {
		String pattern= getPattern();
		SearchPatternData match= findInPrevious(pattern);
		if (match != null) {
			fPreviousSearchPatterns.remove(match);
		}
		match= new SearchPatternData(
				getSearchFor(),
				getLimitTo(),
				pattern,
				fCaseSensitive.getSelection(),
				fJavaElement,
				getContainer().getSelectedScope(),
				getContainer().getSelectedWorkingSets());
			
		fPreviousSearchPatterns.add(0, match);