Implement Document.scrollingElement API behind experimental feature flag

Source/core/dom/Element.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013 Apple Inc. All rights reserved.
  *           (C) 2007 Eric Seidel (eric@webkit.org)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 693 matching lines @@
 
     if (LayoutBox* renderer = layoutBox())
         return adjustLayoutUnitForAbsoluteZoom(renderer->pixelSnappedClientHeight(), *renderer).round();
     return 0;
 }
 
 double Element::scrollLeft()
 {
     document().updateLayoutIgnorePendingStylesheets();
 
-    if (document().documentElement() != this) {
-        if (LayoutBox* box = layoutBox())
-            return adjustScrollForAbsoluteZoom(box->scrollLeft(), *box);
+    if (document().scrollingElement() == this) {
+        if (document().domWindow())
+            return document().domWindow()->scrollX();
         return 0;
     }
 
-    if (RuntimeEnabledFeatures::scrollTopLeftInteropEnabled()) {
-        if (document().inQuirksMode())
-            return 0;
-
-        if (LocalDOMWindow* window = document().domWindow())
-            return window->scrollX();
-    }
+    if (LayoutBox* box = layoutBox())
+        return adjustScrollForAbsoluteZoom(box->scrollLeft(), *box);
 
     return 0;
 }
 
 double Element::scrollTop()
 {
     document().updateLayoutIgnorePendingStylesheets();
 
-    if (document().documentElement() != this) {
-        if (LayoutBox* box = layoutBox())
-            return adjustScrollForAbsoluteZoom(box->scrollTop(), *box);
+    if (document().scrollingElement() == this) {
+        if (document().domWindow())
+            return document().domWindow()->scrollY();
         return 0;
     }
 
-    if (RuntimeEnabledFeatures::scrollTopLeftInteropEnabled()) {
-        if (document().inQuirksMode())
-            return 0;
-
-        if (LocalDOMWindow* window = document().domWindow())
-            return window->scrollY();
-    }
+    if (LayoutBox* box = layoutBox())
+        return adjustScrollForAbsoluteZoom(box->scrollTop(), *box);
 
     return 0;
 }
 
 void Element::setScrollLeft(double newLeft)
 {
     document().updateLayoutIgnorePendingStylesheets();
 
     if (std::isnan(newLeft))
         return;
 
-    if (document().documentElement() != this) {
+    if (document().scrollingElement() == this) {
+        if (LocalDOMWindow* window = document().domWindow())
+            window->scrollTo(newLeft, window->scrollY());
+    } else {
         LayoutBox* box = layoutBox();
         if (box)
             box->setScrollLeft(LayoutUnit::fromFloatRound(newLeft * box->style()->effectiveZoom()));
-        return;
-    }
-
-    if (RuntimeEnabledFeatures::scrollTopLeftInteropEnabled()) {
-        if (document().inQuirksMode())
-            return;
-
-        if (LocalDOMWindow* window = document().domWindow())
-            window->scrollTo(newLeft, window->scrollY());
     }
 }
 
 void Element::setScrollTop(double newTop)
 {
     document().updateLayoutIgnorePendingStylesheets();
 
     if (std::isnan(newTop))
         return;
 
-    if (document().documentElement() != this) {
+    if (document().scrollingElement() == this) {
+        if (LocalDOMWindow* window = document().domWindow())
+            window->scrollTo(window->scrollX(), newTop);
+    } else {
         LayoutBox* box = layoutBox();
         if (box)
             box->setScrollTop(LayoutUnit::fromFloatRound(newTop * box->style()->effectiveZoom()));
-        return;
-    }
-
-    if (RuntimeEnabledFeatures::scrollTopLeftInteropEnabled()) {
-        if (document().inQuirksMode())
-            return;
-
-        if (LocalDOMWindow* window = document().domWindow())
-            window->scrollTo(window->scrollX(), newTop);
     }
 }
 
 int Element::scrollWidth()
 {
     document().updateLayoutIgnorePendingStylesheets();
+
+    if (document().scrollingElement() == this) {
+        if (document().view())
+            return adjustForAbsoluteZoom(document().view()->contentsWidth(), document().frame()->pageZoomFactor());
+        return 0;
+    }
+
     if (LayoutBox* box = layoutBox())
         return adjustLayoutUnitForAbsoluteZoom(box->scrollWidth(), *box).round();
     return 0;
 }
 
 int Element::scrollHeight()
 {
     document().updateLayoutIgnorePendingStylesheets();
+
+    if (document().scrollingElement() == this) {
+        if (document().view())
+            return adjustForAbsoluteZoom(document().view()->contentsHeight(), document().frame()->pageZoomFactor());
+        return 0;
+    }
+
     if (LayoutBox* box = layoutBox())
         return adjustLayoutUnitForAbsoluteZoom(box->scrollHeight(), *box).round();
     return 0;
 }
 
 void Element::scrollBy(double x, double y)
 {
     ScrollToOptions scrollToOptions;
     scrollToOptions.setLeft(x);
     scrollToOptions.setTop(y);
     scrollBy(scrollToOptions);
 }
 
 void Element::scrollBy(const ScrollToOptions& scrollToOptions)
 {
     // FIXME: This should be removed once scroll updates are processed only after
     // the compositing update. See http://crbug.com/420741.
     document().updateLayoutIgnorePendingStylesheets();
 
-    if (document().documentElement() != this) {
+    if (document().scrollingElement() == this) {
+        scrollFrameBy(scrollToOptions);
+    } else {
         scrollLayoutBoxBy(scrollToOptions);
-        return;
-    }
-
-    if (RuntimeEnabledFeatures::scrollTopLeftInteropEnabled()) {
-        if (document().inQuirksMode())
-            return;
-        scrollFrameBy(scrollToOptions);
     }
 }
 
 void Element::scrollTo(double x, double y)
 {
     ScrollToOptions scrollToOptions;
     scrollToOptions.setLeft(x);
     scrollToOptions.setTop(y);
     scrollTo(scrollToOptions);
 }
 
 void Element::scrollTo(const ScrollToOptions& scrollToOptions)
 {
     // FIXME: This should be removed once scroll updates are processed only after
     // the compositing update. See http://crbug.com/420741.
     document().updateLayoutIgnorePendingStylesheets();
 
-    if (document().documentElement() != this) {
+    if (document().scrollingElement() == this) {
+        scrollFrameTo(scrollToOptions);
+    } else {
         scrollLayoutBoxTo(scrollToOptions);
-        return;
-    }
-
-    if (RuntimeEnabledFeatures::scrollTopLeftInteropEnabled()) {
-        if (document().inQuirksMode())
-            return;
-        scrollFrameTo(scrollToOptions);
     }
 }
 
 void Element::scrollLayoutBoxBy(const ScrollToOptions& scrollToOptions)
 {
     double left = scrollToOptions.hasLeft() ? scrollToOptions.left() : 0.0;
     double top = scrollToOptions.hasTop() ? scrollToOptions.top() : 0.0;
     if (std::isnan(left) || std::isnan(top))
         return;
 
@@ skipping 2623 matching lines @@
 {
 #if ENABLE(OILPAN)
     if (hasRareData())
         visitor->trace(elementRareData());
     visitor->trace(m_elementData);
 #endif
     ContainerNode::trace(visitor);
 }
 
 } // namespace blink