Refactoring: Extract DocumentInit for capture Document construction parameter.

Source/core/animation/DocumentTimelineTest.cpp

Index: Source/core/animation/DocumentTimelineTest.cpp
diff --git a/Source/core/animation/DocumentTimelineTest.cpp b/Source/core/animation/DocumentTimelineTest.cpp
index bce6c7520a1e7175c009229ca937a98b6462c7b8..ca515be0a69c0302bce6e401724c2eb04d7883f9 100644
--- a/Source/core/animation/DocumentTimelineTest.cpp
+++ b/Source/core/animation/DocumentTimelineTest.cpp
@@ -48,7 +48,7 @@ class DocumentTimelineTest : public ::testing::Test {
 protected:
     virtual void SetUp()
     {
-        document = Document::create(0, KURL());
+        document = Document::create();
         element = Element::create(nullQName() , document.get());
         timeline = DocumentTimeline::create(document.get());
     }