Refactoring: Introduce HTMLImport interface to form import tree.

Source/core/html/HTMLImport.cpp

Index: Source/core/html/HTMLImport.cpp
diff --git a/Source/core/loader/UniqueIdentifier.cpp b/Source/core/html/HTMLImport.cpp
similarity index 86%
copy from Source/core/loader/UniqueIdentifier.cpp
copy to Source/core/html/HTMLImport.cpp
index 0ad56563e3e214a67acd8c53decb085ad4250cb9..8e349be5c3a5688b9b61d29e9d15fb1a90672d44 100644
--- a/Source/core/loader/UniqueIdentifier.cpp
+++ b/Source/core/html/HTMLImport.cpp
@@ -29,16 +29,17 @@
  */
 
 #include "config.h"
-#include "core/loader/UniqueIdentifier.h"
+#include "core/html/HTMLImport.h"
 
-namespace WebCore {
+#include "core/html/HTMLImportsController.h"
 
-static unsigned long s_uniqueIdentifier = 0;
+namespace WebCore {
 
-unsigned long createUniqueIdentifier()
+bool HTMLImport::haveChildrenLoaded()
 {
-    return ++s_uniqueIdentifier;
+    if (HTMLImportsController* controller = this->controller())
+        return controller->haveChildrenLoaded(this);
+    return true;
 }
 
 } // namespace WebCore
-