Add a lifecycle state machine for Document

Source/core/dom/DocumentLifecycle.cpp

Index: Source/core/dom/DocumentLifecycle.cpp
diff --git a/Source/core/html/HTMLMediaSource.cpp b/Source/core/dom/DocumentLifecycle.cpp
similarity index 85%
copy from Source/core/html/HTMLMediaSource.cpp
copy to Source/core/dom/DocumentLifecycle.cpp
index 7221cfeaf34ed4e40fd174029a3fa66a6d8dd411..35af202cf8f6a34ab3f3fb76981cc7af60584ea8 100644
--- a/Source/core/html/HTMLMediaSource.cpp
+++ b/Source/core/dom/DocumentLifecycle.cpp
@@ -29,16 +29,25 @@
  */
 
 #include "config.h"
-#include "core/html/HTMLMediaSource.h"
+#include "core/dom/DocumentLifecycle.h"
+
+#include "wtf/Assertions.h"
 
 namespace WebCore {
 
-URLRegistry* HTMLMediaSource::s_registry = 0;
+DocumentLifecycle::DocumentLifecycle()
+    : m_state(Uninitialized)
+{
+}
+
+DocumentLifecycle::~DocumentLifecycle()
+{
+}
 
-void HTMLMediaSource::setRegistry(URLRegistry* registry)
+void DocumentLifecycle::advanceTo(State state)
 {
-    ASSERT(!s_registry);
-    s_registry = registry;
+    ASSERT(state > m_state);
+    m_state = state;
 }
 
 }