Implement media cast buttons

Source/core/html/shadow/MediaControls.cpp

Index: Source/core/html/shadow/MediaControls.cpp
diff --git a/Source/core/html/shadow/MediaControls.cpp b/Source/core/html/shadow/MediaControls.cpp
index 05c56e8d88923dcd665c1f2f32c593d620b9cc69..721fd111031baaccad660c44b0f98d5350766f9f 100644
--- a/Source/core/html/shadow/MediaControls.cpp
+++ b/Source/core/html/shadow/MediaControls.cpp
@@ -52,6 +52,7 @@ MediaControls::MediaControls(HTMLMediaElement& mediaElement)
     , m_volumeSlider(nullptr)
     , m_toggleClosedCaptionsButton(nullptr)
     , m_fullScreenButton(nullptr)
+    , m_castButton(nullptr)
     , m_durationDisplay(nullptr)
     , m_enclosure(nullptr)
     , m_hideMediaControlsTimer(this, &MediaControls::hideMediaControlsTimerFired)
@@ -136,6 +137,12 @@ bool MediaControls::initializeControls()
     if (exceptionState.hadException())
         return false;
 
+    RefPtrWillBeRawPtr<MediaControlCastOffButtonElement> castButton = MediaControlCastOffButtonElement::create(*this);
+    m_castButton = castButton.get();
+    panel->appendChild(castButton.release(), exceptionState);
+    if (exceptionState.hadException())
+        return false;
+
     RefPtrWillBeRawPtr<MediaControlFullscreenButtonElement> fullscreenButton = MediaControlFullscreenButtonElement::create(*this);
     m_fullScreenButton = fullscreenButton.get();
     panel->appendChild(fullscreenButton.release(), exceptionState);
@@ -181,6 +188,8 @@ void MediaControls::reset()
     else
         m_fullScreenButton->hide();
 
+    m_castButton->show();
+
     makeOpaque();
 }