LayoutTests/imported/w3c/web-platform-tests/user-timing/clear_one_mark.any.js

test(function() {
    self.performance.mark("mark1");
    self.performance.mark("mark2");

    // test that two marks have been created
    var entries = self.performance.getEntriesByType("mark");
    assert_equals(entries.length, 2, "Two marks have been created for this test.");

    // clear existent mark
    self.performance.clearMarks("mark1");

    // test that "mark1" was cleared
    entries = self.performance.getEntriesByName("mark1");

    assert_equals(entries.length, 0,
              "After a call to self.performance.clearMarks(\"mark1\"), " +
              "window.performance.getEntriesByName(\"mark1\") returns an empty object.");

    // test that "mark2" still exists
    entries = self.performance.getEntriesByName("mark2");
    assert_equals(entries[0].name, "mark2",
              "After a call to self.performance.clearMarks(\"mark1\"), " +
              "window.performance.getEntriesByName(\"mark2\") returns an object containing the " +
              "\"mark2\" mark.");

}, "Clearing an existent mark doesn't affect other existing marks");