LayoutFullScreen::m_placeholder is LayoutBlockFlow.

third_party/WebKit/Source/core/dom/Fullscreen.cpp

Index: third_party/WebKit/Source/core/dom/Fullscreen.cpp
diff --git a/third_party/WebKit/Source/core/dom/Fullscreen.cpp b/third_party/WebKit/Source/core/dom/Fullscreen.cpp
index 9b931c8f972e72b2a50c95120340873cf7342b7f..bd4cda9a7616dadc8899a26cef5aa7f347ccdcca 100644
--- a/third_party/WebKit/Source/core/dom/Fullscreen.cpp
+++ b/third_party/WebKit/Source/core/dom/Fullscreen.cpp
@@ -42,6 +42,7 @@
 #include "core/html/HTMLMediaElement.h"
 #include "core/input/EventHandler.h"
 #include "core/inspector/ConsoleMessage.h"
+#include "core/layout/LayoutBlockFlow.h"
 #include "core/layout/LayoutFullScreen.h"
 #include "core/layout/api/LayoutFullScreenItem.h"
 #include "core/page/ChromeClient.h"
@@ -498,7 +499,7 @@ void Fullscreen::setFullScreenLayoutObject(LayoutFullScreen* layoutObject)
     if (layoutObject && m_savedPlaceholderComputedStyle) {
         layoutObject->createPlaceholder(m_savedPlaceholderComputedStyle.release(), m_savedPlaceholderFrameRect);
     } else if (layoutObject && m_fullScreenLayoutObject && m_fullScreenLayoutObject->placeholder()) {
-        LayoutBlock* placeholder = m_fullScreenLayoutObject->placeholder();
+        LayoutBlockFlow* placeholder = m_fullScreenLayoutObject->placeholder();
         layoutObject->createPlaceholder(ComputedStyle::clone(placeholder->styleRef()), placeholder->frameRect());
     }