HTML Imports: Teach preloader about HTML Imports.

Source/core/testing/Internals.cpp

Index: Source/core/testing/Internals.cpp
diff --git a/Source/core/testing/Internals.cpp b/Source/core/testing/Internals.cpp
index 5b224b03dfae57481a9c25238f15656f8497404a..284d4f1655b4dfc8462a1074c93cb76ebe93cefd 100644
--- a/Source/core/testing/Internals.cpp
+++ b/Source/core/testing/Internals.cpp
@@ -320,7 +320,13 @@ unsigned Internals::hitTestCount(Document* doc, ExceptionState& exceptionState)
 
 bool Internals::isPreloaded(const String& url)
 {
-    Document* document = contextDocument();
+    return isPreloadedBy(url, contextDocument());
+}
+
+bool Internals::isPreloadedBy(const String& url, Document* document)
+{
+    if (!document)
+        return false;
     return document->fetcher()->isPreloaded(document->completeURL(url));
 }