Reland of "Move UndoStack from Page to Editor"

third_party/WebKit/Source/core/loader/FrameLoader.cpp

Index: third_party/WebKit/Source/core/loader/FrameLoader.cpp
diff --git a/third_party/WebKit/Source/core/loader/FrameLoader.cpp b/third_party/WebKit/Source/core/loader/FrameLoader.cpp
index 2e480c0c4290bfb72f1189103f626fb446adbe82..3c0b05372ee511a50e060072501e7b289e7a20e2 100644
--- a/third_party/WebKit/Source/core/loader/FrameLoader.cpp
+++ b/third_party/WebKit/Source/core/loader/FrameLoader.cpp
@@ -42,7 +42,6 @@
 #include "core/dom/Element.h"
 #include "core/dom/ViewportDescription.h"
 #include "core/editing/Editor.h"
-#include "core/editing/commands/UndoStack.h"
 #include "core/events/GestureEvent.h"
 #include "core/events/KeyboardEvent.h"
 #include "core/events/MouseEvent.h"
@@ -270,8 +269,7 @@ void FrameLoader::dispatchUnloadEvent()
     if (m_frame->document() && !SVGImage::isInSVGImage(m_frame->document()))
         m_frame->document()->dispatchUnloadEvents();
 
-    if (Page* page = m_frame->page())
-        page->undoStack().didUnloadFrame(*m_frame);
+    m_frame->editor().clearUndoStack();
 }
 
 void FrameLoader::didExplicitOpen()