Improve CancellableTaskFactory handling and Oilpan usage.

Source/core/dom/Document.h

Index: Source/core/dom/Document.h
diff --git a/Source/core/dom/Document.h b/Source/core/dom/Document.h
index df56047701d40d35a262e27db742e2dc5bf72737..bbe68f965dac9555a952bade4edbecde41b85551 100644
--- a/Source/core/dom/Document.h
+++ b/Source/core/dom/Document.h
@@ -57,7 +57,6 @@
 #include "platform/Length.h"
 #include "platform/Timer.h"
 #include "platform/heap/Handle.h"
-#include "platform/scheduler/CancellableTaskFactory.h"
 #include "platform/weborigin/KURL.h"
 #include "platform/weborigin/ReferrerPolicy.h"
 #include "public/platform/WebFocusType.h"
@@ -75,6 +74,7 @@ class Attr;
 class CDATASection;
 class CSSStyleDeclaration;
 class CSSStyleSheet;
+class CancellableTaskFactory;
 class CanvasFontCache;
 class CanvasRenderingContext2D;
 class CanvasRenderingContext2DOrWebGLRenderingContext;
@@ -1200,7 +1200,7 @@ private:
     CompatibilityMode m_compatibilityMode;
     bool m_compatibilityModeLocked; // This is cheaper than making setCompatibilityMode virtual.
 
-    CancellableTaskFactory m_executeScriptsWaitingForResourcesTask;
+    OwnPtr<CancellableTaskFactory> m_executeScriptsWaitingForResourcesTask;
 
     bool m_hasAutofocused;
     Timer<Document> m_clearFocusedElementTimer;