Improve caption button behavior for video player.

third_party/WebKit/LayoutTests/media/media-controls.js

 var captionsButtonElement;
 var captionsButtonCoordinates;
 
 // As specified in mediaControls.css, this is how long it takes to fade out controls
 const controlsFadeOutDurationMs = 300;
 
 // The timeout for the hide-after-no-mouse-movement behavior. Defined (and
 // should mirror) the value 'timeWithoutMouseMovementBeforeHidingMediaControls'
 // in MediaControls.cpp.
 const controlsMouseMovementTimeoutMs = 3000;
@@ skipping 115 matching lines @@
 function clickAtCoordinates(x, y)
 {
     eventSender.mouseMoveTo(x, y);
     eventSender.mouseDown();
     eventSender.mouseUp();
 }
 
 function textTrackListItemAtIndex(video, index)
 {
     var textTrackListElementID = "-internal-media-controls-text-track-list";
-    var textTrackListElement = mediaControlsElement(internals.shadowRoot(video).firstChild, textTrackListElementID);
+    var textTrackListElement = mediaControlsElement(
+            internals.shadowRoot(video).firstChild, textTrackListElementID);
     if (!textTrackListElement)
         throw "Failed to find text track list element";
 
     var trackListItems = textTrackListElement.childNodes;
     for (var i = 0; i < trackListItems.length; i++) {
         var trackListItem = trackListItems[i];
         if (trackListItem.firstChild.getAttribute("data-track-index") == index)
             return trackListItem;
     }
 }
 
+function clickCaptionButton(video)
+{
+    var captionsButtonCoordinates =
+            mediaControlsButtonCoordinates(video, "toggle-closed-captions-button");
+    clickAtCoordinates(captionsButtonCoordinates[0], captionsButtonCoordinates[1]);
+}
+
 function clickTextTrackAtIndex(video, index)
 {
-    var captionsButtonCoordinates = mediaControlsButtonCoordinates(video, "toggle-closed-captions-button");
-    clickAtCoordinates(captionsButtonCoordinates[0], captionsButtonCoordinates[1]);
+    clickCaptionButton(video);
     var trackListItemElement = textTrackListItemAtIndex(video, index);
     var trackListItemCoordinates = elementCoordinates(trackListItemElement);
     clickAtCoordinates(trackListItemCoordinates[0], trackListItemCoordinates[1]);
 }
 
 function turnClosedCaptionsOff(video)
 {
     clickTextTrackAtIndex(video, -1);
 }
 
+function checkCaptionsVisible(video, captions)
+{
+    for (var i = 0; i < captions.length; i++) {
+      assert_equals(textTrackCueElementByIndex(video, i).innerText, captions[i]);
+    }
+}
+
+function checkCaptionsHidden(video)
+{
+    assert_equals(textTrackDisplayElement(video), null);
+}
+
 function runAfterHideMediaControlsTimerFired(func, mediaElement)
 {
     if (mediaElement.paused)
         throw "The media element is not playing";
 
     // Compute the time it'll take until the controls will be invisible -
     // assuming playback has been started prior to invoking this
     // function. Allow 500ms slack.
     var hideTimeoutMs = controlsMouseMovementTimeoutMs + controlsFadeOutDurationMs + 500;
 
     if (!mediaElement.loop && hideTimeoutMs >= 1000 * (mediaElement.duration - mediaElement.currentTime))
         throw "The media will end before the controls have been hidden";
 
     setTimeout(func, hideTimeoutMs);
 }
 
 function hasFullscreenButton(element)
 {
     var size = mediaControlsButtonDimensions(element, "fullscreen-button");
     return size[0] > 0 && size[1] > 0;
 }