Bug 65378 FindOccurencesCUEngine should use ASTProvider
RC1 FindOccurrencesEngine should get the AST from the ASTProvider so it can profit if the AST is already cached (2 occurences) e.g. JaavPlugin.getDefault().getASTProvider().getAST(cu)
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/search/FindOccurrencesEngine.java
protected IOccurrencesFinder getOccurrencesFinder() {
		return fFinder;
	}
	public String run(int offset, int length) throws JavaModelException {
		ISourceReference sr= getSourceReference();
		if (sr.getSourceRange() == null) {
			return SearchMessages.getString("FindOccurrencesEngine.noSource.text");  
		}
		
		final CompilationUnit root= createAST();
		if (root == null) {
			return SearchMessages.getString("FindOccurrencesEngine.cannotParse.text"); 
		}
		String message= fFinder.initialize(root, offset, length);
		if (message != null)
			return message;
		
		final IDocument document= new Document(getSourceReference().getSource());
		
		if (USE_NEW_SEARCH) {
			performNewSearch(fFinder, document, getInput());
			return null;
		}
		
		final IWorkspaceRunnable runnable= new IWorkspaceRunnable() {
			public void run(IProgressMonitor monitor) throws CoreException {
				ISearchResultView view= startSearch();
				fFinder.perform();
				IResource file= getMarkerOwner();				
				IMarker[] markers= fFinder.createMarkers(file, document);