Simplify MediaControls::show() and hide()

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 2af3e93524f5377ae83bfa9e3f968527fd9c6192..f4ae8fe9c2c1a91dbf4d652859cc59805c56cd29 100644
--- a/Source/core/html/shadow/MediaControls.cpp
+++ b/Source/core/html/shadow/MediaControls.cpp
@@ -27,6 +27,7 @@
 #include "config.h"
 #include "core/html/shadow/MediaControls.h"
 
+#include "HTMLNames.h"
 #include "bindings/v8/ExceptionStatePlaceholder.h"
 #include "core/events/MouseEvent.h"
 #include "core/html/HTMLMediaElement.h"
@@ -201,15 +202,13 @@ void MediaControls::reset()
 
 void MediaControls::show()
 {
+    setBooleanAttribute(HTMLNames::hiddenAttr, false);
     makeOpaque();
-    m_panel->setIsDisplayed(true);
-    m_panel->show();
 }
 
 void MediaControls::hide()
 {
-    m_panel->setIsDisplayed(false);
-    m_panel->hide();
+    setBooleanAttribute(HTMLNames::hiddenAttr, true);
 }
 
 void MediaControls::makeOpaque()