Use counters for opacity with transform-style:preserve-3d

third_party/WebKit/Source/core/layout/compositing/GraphicsLayerUpdater.cpp

Index: third_party/WebKit/Source/core/layout/compositing/GraphicsLayerUpdater.cpp
diff --git a/third_party/WebKit/Source/core/layout/compositing/GraphicsLayerUpdater.cpp b/third_party/WebKit/Source/core/layout/compositing/GraphicsLayerUpdater.cpp
index 5c690c9beb034319646c20b102ee3c638d26bbb8..a88057974a405541d64de5e618a1cf54d201d0f5 100644
--- a/third_party/WebKit/Source/core/layout/compositing/GraphicsLayerUpdater.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/GraphicsLayerUpdater.cpp
@@ -103,6 +103,10 @@ void GraphicsLayerUpdater::updateRecursive(PaintLayer& layer, UpdateType updateT
                 scrollableArea->positionOverflowControls();
             updateType = mapping->updateTypeForChildren(updateType);
             mapping->clearNeedsGraphicsLayerUpdate();
+
+            const ComputedStyle& style = layer.layoutObject()->styleRef();
+            if (style.preserves3D() && style.hasOpacity() && layer.has3DTransformedDescendant())

[chrishtr, 2016/05/18 23:16:03]

Does this account for whether the child flattens itself, as opposed to being
inside the same preserves-3d
space as this element?

[chrishtr, 2016/05/18 23:22:10]

Also, I was expecting this usecounter to be in
CLM::updateGraphicsLayerConfiguration.

[trchen, 2016/05/19 00:33:28]

Done.

+                UseCounter::count(layer.layoutObject()->document(), UseCounter::OpacityWithPreserve3DQuirk);
         }
     }