code: @VisibleForTesting
      ReviewResult filterResults(ReviewResult results, Review review) {
          ReviewResult filteredResults = new ReviewResult();
          Set<String> reviewFiles = new HashSet<>();
          for (ReviewFile file : review.getFiles()) {
              reviewFiles.add(file.getReviewFilename());
          }
          for (Violation violation : results.getViolations()) {
              if (reviewFiles.contains(violation.getFilenameOrJavaClassName())) {
                  filteredResults.add(violation);
              }
          }
          return filteredResults;
      }
docs: Filters a ReviewResult to keep only the violations that are about a file
  which is modified by a given review.