Remove TextTrackClient interface to simplify TextTrack code.

Source/core/html/HTMLMediaElement.cpp

Index: Source/core/html/HTMLMediaElement.cpp
diff --git a/Source/core/html/HTMLMediaElement.cpp b/Source/core/html/HTMLMediaElement.cpp
index e3200b99eacee293ebc73b40926156db4e053c64..c29db43fe2fce58978447d987cd280745fed3926 100644
--- a/Source/core/html/HTMLMediaElement.cpp
+++ b/Source/core/html/HTMLMediaElement.cpp
@@ -333,7 +333,7 @@ HTMLMediaElement::~HTMLMediaElement()
     setShouldDelayLoadEvent(false);
 
     if (m_textTracks)
-        m_textTracks->clearOwnerAndClients();
+        m_textTracks->clearOwner();
 
     if (m_mediaController) {
         m_mediaController->removeMediaElement(this);
@@ -2489,7 +2489,7 @@ void HTMLMediaElement::mediaPlayerDidAddTextTrack(WebInbandTextTrack* webTrack)
 
     // 4.8.10.12.2 Sourcing in-band text tracks
     // 1. Associate the relevant data with a new text track and its corresponding new TextTrack object.
-    RefPtr<InbandTextTrack> textTrack = InbandTextTrack::create(document(), this, webTrack);
+    RefPtr<InbandTextTrack> textTrack = InbandTextTrack::create(document(), webTrack);
 
     // 2. Set the new text track's kind, label, and language based on the semantics of the relevant data,
     // as defined by the relevant specification. If there is no label in that data, then the label must
@@ -2583,7 +2583,7 @@ PassRefPtr<TextTrack> HTMLMediaElement::addTextTrack(const AtomicString& kind, c
 
     // 5. Create a new text track corresponding to the new object, and set its text track kind to kind, its text
     // track label to label, its text track language to language...
-    RefPtr<TextTrack> textTrack = TextTrack::create(document(), this, kind, label, language);
+    RefPtr<TextTrack> textTrack = TextTrack::create(document(), kind, label, language);
 
     // Note, due to side effects when changing track parameters, we have to
     // first append the track to the text track list.