compositor-worker: plumb element id and mutable properties

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 57 matching lines @@
 #include "core/page/Page.h"
 #include "core/page/scrolling/ScrollingCoordinator.h"
 #include "core/paint/PaintLayerFragment.h"
 #include "platform/PlatformGestureEvent.h"
 #include "platform/PlatformMouseEvent.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/graphics/paint/DrawingRecorder.h"
 #include "platform/scroll/ScrollAnimatorBase.h"
 #include "platform/scroll/ScrollbarTheme.h"
 #include "public/platform/Platform.h"
+#include "public/platform/WebCompositorMutableProperties.h"
 
 namespace blink {
 
 const int ResizerControlExpandRatioForTouch = 2;
 
 PaintLayerScrollableArea::PaintLayerScrollableArea(PaintLayer& layer)
     : m_layer(layer)
     , m_inResizeMode(false)
     , m_scrollsOverflow(false)
     , m_inOverflowRelayout(false)
@@ skipping 1342 matching lines @@
     if (box().isIntrinsicallyScrollable(VerticalScrollbar) || box().isIntrinsicallyScrollable(HorizontalScrollbar))
         return false;
 
     // See https://codereview.chromium.org/176633003/ for the tests that fail without this disabler.
     DisableCompositingQueryAsserts disabler;
     return layer()->hasCompositedLayerMapping() && layer()->compositedLayerMapping()->scrollingLayer();
 }
 
 static bool layerNeedsCompositedScrolling(PaintLayerScrollableArea::LCDTextMode mode, const PaintLayer* layer)
 {
+    if (!layer->scrollsOverflow())
+        return false;
+
+    Node* node = layer->enclosingElement();
+    if (node && node->isElementNode() && (toElement(node)->mutableProperties() & (WebCompositorMutablePropertyScrollTop | WebCompositorMutablePropertyScrollLeft)))
+        return true;
+
     if (mode == PaintLayerScrollableArea::ConsiderLCDText && !layer->compositor()->preferCompositingToLCDTextEnabled())
         return false;
 
-    return layer->scrollsOverflow()
-        && !layer->hasDescendantWithClipPath()
+    return !layer->hasDescendantWithClipPath()
         && !layer->hasAncestorWithClipPath()
         && !layer->layoutObject()->style()->hasBorderRadius();
 }
 
 void PaintLayerScrollableArea::updateNeedsCompositedScrolling(LCDTextMode mode)
 {
     const bool needsCompositedScrolling = layerNeedsCompositedScrolling(mode, layer());
     if (static_cast<bool>(m_needsCompositedScrolling) != needsCompositedScrolling) {
         m_needsCompositedScrolling = needsCompositedScrolling;
         layer()->didUpdateNeedsCompositedScrolling();
@@ skipping 121 matching lines @@
 }
 
 DEFINE_TRACE(PaintLayerScrollableArea::ScrollbarManager)
 {
     visitor->trace(m_scrollableArea);
     visitor->trace(m_hBar);
     visitor->trace(m_vBar);
 }
 
 } // namespace blink