set and get scrollTop/Left through documentElement and body should be symmetric, according to the d…

Source/core/dom/Element.cpp

Index: Source/core/dom/Element.cpp
diff --git a/Source/core/dom/Element.cpp b/Source/core/dom/Element.cpp
index 295cd9fbd11ba889a4b3ea5cb7741a1f3759ccc6..fc9327d408afbc15ad84f4bf41637b1a66d1a9af 100644
--- a/Source/core/dom/Element.cpp
+++ b/Source/core/dom/Element.cpp
@@ -724,6 +724,20 @@ int Element::scrollTop()
 void Element::setScrollLeft(int newLeft)
 {
     document().updateLayoutIgnorePendingStylesheets();
+
+    if (document().documentElement() == this) {
+        if (document().inQuirksMode())
+            return;
+
+        Frame* frame = document().frame();
+        if (!frame)
+            return;
+        FrameView* view = frame->view();
+        if (!view)
+            return;
+        view->setScrollPosition(IntPoint(static_cast<int>(newLeft * frame->pageZoomFactor()), view->scrollY()));

[Julien - ping for review, 2013/10/05 01:05:46]

The specification is weird and seem to imply that you shouldn't put scrollY() as
the second parameter here:

"4. If the element is the root element invoke scroll() with x as first argument
and zero as second, and, if the given value is a ScrollOptionsHorizontal object,
the given value as the third argument."

Am I missing something obvious here?

+    }
+
     if (RenderBox* rend = renderBox())
         rend->setScrollLeft(static_cast<int>(newLeft * rend->style()->effectiveZoom()));
 }
@@ -731,6 +745,20 @@ void Element::setScrollLeft(int newLeft)
 void Element::setScrollTop(int newTop)
 {
     document().updateLayoutIgnorePendingStylesheets();
+
+    if (document().documentElement() == this) {
+        if (document().inQuirksMode())
+            return;
+
+        Frame* frame = document().frame();
+        if (!frame)
+            return;
+        FrameView* view = frame->view();
+        if (!view)
+            return;
+        view->setScrollPosition(IntPoint(view->scrollX(), static_cast<int>(newTop * frame->pageZoomFactor())));
+    }
+
     if (RenderBox* rend = renderBox())
         rend->setScrollTop(static_cast<int>(newTop * rend->style()->effectiveZoom()));
 }