Updates volume to change by .05 increments.

third_party/WebKit/LayoutTests/media/controls/controls-video-keynav.html

 <DOCTYPE html>
 <title>Test media controls video keyboard navigation</title>
 <script src="../../resources/testharness.js"></script>
 <script src="../../resources/testharnessreport.js"></script>
 <script src="../media-file.js"></script>
 <script src="../media-controls.js"></script>
 <video controls></video>
 <script>
 test(_ => {
   assert_true('eventSender' in window);
 }, 'eventSender required');
 
 async_test(function(t) {
     var video = document.querySelector("video");
     video.src = findMediaFile("video", "../content/test");
     assert_equals(video.volume, 1);
     assert_equals(video.currentTime, 0);
 
     video.oncanplaythrough = t.step_func_done(function() {
       // Focus the video.
       video.focus();
 
       // 'Enter' plays the video.
       eventSender.keyDown("Enter");
       assert_false(video.paused);
 
-      // 'Down' reduces volume.
+      // 'Down' reduces volume by .05.
       eventSender.keyDown("ArrowDown");
-      assert_less_than(video.volume, 1);
+      assert_equals(video.volume, .95);
 
-      // 'Up' increases volume.
+      eventSender.keyDown("ArrowDown");
+      assert_equals(video.volume, .9);
+
+      // 'Up' increases volume by .05
+      eventSender.keyDown("ArrowUp");
+      assert_equals(video.volume, .95);
+
       eventSender.keyDown("ArrowUp");
       assert_equals(video.volume, 1);
 
       // 'Enter' again pauses the video.
       eventSender.keyDown("Enter");
       assert_true(video.paused);
 
       // 'Space' also pauses/plays the video.
       eventSender.keyDown(" ");
       assert_false(video.paused);
@@ skipping 16 matching lines @@
       // 'End' sets the timeline to end.
       eventSender.keyDown("End");
       assert_equals(video.currentTime, video.duration);
 
       // 'Left' scrubs the timeline back.
       eventSender.keyDown("ArrowLeft");
       assert_less_than(video.currentTime, video.duration);
     });
 });
 </script>