Use a ResizeObserver to determine default font-size for text tracks

third_party/WebKit/Source/core/html/HTMLMediaElement.cpp

 /*
  * Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights
  * reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 3645 matching lines @@
 }
 
 TextTrackContainer& HTMLMediaElement::EnsureTextTrackContainer() {
   ShadowRoot& shadow_root = EnsureUserAgentShadowRoot();
   AssertShadowRootChildren(shadow_root);
 
   Node* first_child = shadow_root.FirstChild();
   if (first_child && first_child->IsTextTrackContainer())
     return ToTextTrackContainer(*first_child);
 
-  TextTrackContainer* text_track_container =
-      TextTrackContainer::Create(GetDocument());
+  TextTrackContainer* text_track_container = TextTrackContainer::Create(*this);
 
   // The text track container should be inserted before the media controls,
   // so that they are rendered behind them.
   shadow_root.InsertBefore(text_track_container, first_child);
 
   AssertShadowRootChildren(shadow_root);
 
   return *text_track_container;
 }
 
@@ skipping 591 matching lines @@
       kMostlyFillViewportBecomeStableSeconds, BLINK_FROM_HERE);
 }
 
 void HTMLMediaElement::ViewportFillDebouncerTimerFired(TimerBase*) {
   mostly_filling_viewport_ = true;
   if (web_media_player_)
     web_media_player_->BecameDominantVisibleContent(mostly_filling_viewport_);
 }
 
 }  // namespace blink