Use C++11 features in core/html

Source/core/html/shadow/MediaControlElementTypes.cpp

Index: Source/core/html/shadow/MediaControlElementTypes.cpp
diff --git a/Source/core/html/shadow/MediaControlElementTypes.cpp b/Source/core/html/shadow/MediaControlElementTypes.cpp
index 375a8def79da84a73d05a287102ec9a9244c7fbe..ae225d6e7476269dc45899072ff73381ee95a96c 100644
--- a/Source/core/html/shadow/MediaControlElementTypes.cpp
+++ b/Source/core/html/shadow/MediaControlElementTypes.cpp
@@ -48,12 +48,12 @@ class Event;
 HTMLMediaElement* toParentMediaElement(Node* node)
 {
     if (!node)
-        return 0;
+        return nullptr;
     Node* mediaNode = node->shadowHost();
     if (!mediaNode)
-        return 0;
+        return nullptr;
     if (!isHTMLMediaElement(mediaNode))
-        return 0;
+        return nullptr;
 
     return toHTMLMediaElement(mediaNode);
 }