Refactor textTractDisplayElement utility function

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 70 matching lines @@
 function textTrackCueElementByIndex(parentElement, cueIndex) {
     var displayElement = textTrackCueDisplayElement(parentElement);
     if (displayElement) {
         for (i = 0; i < cueIndex; i++)
             displayElement = displayElement.nextSibling;
     }
 
     return displayElement;
 }
 
+function textTrackRegionElement(parentElement)
+{
+    var containerElement = textTrackContainerElement(parentElement);
+    return mediaControlsElement(containerElement.firstChild, "-webkit-media-text-track-region");
+}
+
+function textTrackRegionContainerElement(parentElement)
+{
+    var containerElement = textTrackContainerElement(parentElement);
+    return mediaControlsElement(containerElement.firstChild, "-webkit-media-text-track-region-container");
+}
+
 // TODO(srirama.m): Phase out the uses of this function and
 // replace with more specific functions at each call site.
-// For ex: textTrackDisplayElement(video, 'region') => textTrackRegionElement(video) and
-// textTrackDisplayElement(video, 'region-container') => textTrackRegionContainerElement(video).
 function textTrackDisplayElement(parentElement, id, cueNumber)
 {
     var containerElement = textTrackContainerElement(parentElement);
 
     if (!containerElement)
         throw "Failed to find text track container element";
 
     if (!id)
         return containerElement;
 
@@ skipping 80 matching lines @@
         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;
 }