Remove usesCompositedScrolling

sky/engine/core/rendering/RenderLayerScrollableArea.cpp

Index: sky/engine/core/rendering/RenderLayerScrollableArea.cpp
diff --git a/sky/engine/core/rendering/RenderLayerScrollableArea.cpp b/sky/engine/core/rendering/RenderLayerScrollableArea.cpp
index e987c40bf7506e73b0ff7e58d38c82fe91547c70..9106226c500744c2f256b22635148466c6e0bb47 100644
--- a/sky/engine/core/rendering/RenderLayerScrollableArea.cpp
+++ b/sky/engine/core/rendering/RenderLayerScrollableArea.cpp
@@ -306,7 +306,7 @@ void RenderLayerScrollableArea::setScrollOffset(const IntPoint& newScrollOffset)
             && !layer()->hasBlockSelectionGapBounds()
             && box().style()->backgroundLayers().attachment() != LocalBackgroundAttachment;
 
-        if (usesCompositedScrolling() || onlyScrolledCompositedLayers)
+        if (onlyScrolledCompositedLayers)

[rafaelw, 2014/11/07 19:41:48]

Given the name of this bool, I might guess that this entire block should go away
and we should always just require paint invalidation below, but I can't tell if
that's safe.

[abarth-chromium, 2014/11/07 19:44:23]

That sounds right.

             requiresPaintInvalidation = false;
     }
 
@@ -388,9 +388,6 @@ IntRect RenderLayerScrollableArea::scrollableAreaBoundingBox() const
 
 bool RenderLayerScrollableArea::userInputScrollable(ScrollbarOrientation orientation) const
 {
-    if (box().isIntristicallyScrollable(orientation))
-        return true;
-
     EOverflow overflowStyle = (orientation == HorizontalScrollbar) ?
         box().style()->overflowX() : box().style()->overflowY();
     return (overflowStyle == OSCROLL || overflowStyle == OAUTO || overflowStyle == OOVERLAY);
@@ -910,28 +907,10 @@ void RenderLayerScrollableArea::updateCompositingLayersAfterScroll()
 {
     RenderLayerCompositor* compositor = box().view()->compositor();
     if (compositor->inCompositingMode()) {
-        if (usesCompositedScrolling()) {
-            DisableCompositingQueryAsserts disabler;
-            ASSERT(layer()->hasCompositedLayerMapping());
-            layer()->compositedLayerMapping()->setNeedsGraphicsLayerUpdate(GraphicsLayerUpdateSubtree);
-            compositor->setNeedsCompositingUpdate(CompositingUpdateAfterGeometryChange);
-        } else {
-            layer()->setNeedsCompositingInputsUpdate();
-        }
+        layer()->setNeedsCompositingInputsUpdate();
     }
 }
 
-bool RenderLayerScrollableArea::usesCompositedScrolling() const
-{
-    // Scroll form controls on the main thread so they exhibit correct touch scroll event bubbling
-    if (box().isIntristicallyScrollable(VerticalScrollbar) || box().isIntristicallyScrollable(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(const RenderLayer* layer)
 {
     return layer->scrollsOverflow()