[SPv2] Add CSS mix-blend-mode support

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/paint/PaintPropertyTreeBuilder.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
 #include "core/layout/LayoutInline.h"
@@ skipping 350 matching lines @@
       context.current.shouldFlattenInheritedTransform = true;
     }
   }
 }
 
 void PaintPropertyTreeBuilder::updateEffect(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
   const ComputedStyle& style = object.styleRef();
 
+  // TODO(crbug.com/673500): style.isStackingContext() is only meaningful for
+  // HTML elements. What we really want to ask is whether the element starts
+  // an isolated group, and SVGs use a different rule.
   if (!style.isStackingContext()) {
     if (object.needsPaintPropertyUpdate() || context.forceSubtreeUpdate) {
       if (auto* properties = object.getMutableForPainting().paintProperties())
         context.forceSubtreeUpdate |= properties->clearEffect();
     }
     return;
   }
 
   // TODO(trchen): Can't omit effect node if we have 3D children.
-  // TODO(trchen): Can't omit effect node if we have blending children.
   if (object.needsPaintPropertyUpdate() || context.forceSubtreeUpdate) {
     bool effectNodeNeeded = false;
 
+    // Can't omit effect node if we have paint children with exotic blending.
+    if (object.isSVG()) {
+      // Yes, including LayoutSVGRoot, because SVG layout objects don't create
+      // PaintLayer so PaintLayer::hasNonIsolatedDescendantWithBlendMode()
+      // doesn't catch SVG descendants.
+      if (object.hasNonIsolatedBlendingDescendants())
+        effectNodeNeeded = true;
+    } else if (PaintLayer* layer = toLayoutBoxModelObject(object).layer()) {
+      if (layer->hasNonIsolatedDescendantWithBlendMode())
+        effectNodeNeeded = true;
+    }
+
+    SkBlendMode blendMode =
+        WebCoreCompositeToSkiaComposite(CompositeSourceOver, style.blendMode());
+    if (blendMode != SkBlendMode::kSrcOver)
+      effectNodeNeeded = true;
+
     float opacity = style.opacity();
     if (opacity != 1.0f)
       effectNodeNeeded = true;
 
     CompositorFilterOperations filter;
     if (object.isSVG() && !object.isSVGRoot()) {
       // TODO(trchen): SVG caches filters in SVGResources. Implement it.
     } else if (PaintLayer* layer = toLayoutBoxModelObject(object).layer()) {
       // TODO(trchen): Eliminate PaintLayer dependency.
       filter = layer->createCompositorFilterOperationsForFilter(style);
@@ skipping 24 matching lines @@
 
       // TODO(trchen): A filter may contain spatial operations such that an
       // output pixel may depend on an input pixel outside of the output clip.
       // We should generate a special clip node to represent this expansion.
     }
 
     if (effectNodeNeeded) {
       auto& properties = object.getMutableForPainting().ensurePaintProperties();
       context.forceSubtreeUpdate |= properties.updateEffect(
           context.currentEffect, context.current.transform, outputClip,
-          std::move(filter), opacity);
+          std::move(filter), opacity, blendMode);
     } else {
       if (auto* properties = object.getMutableForPainting().paintProperties())
         context.forceSubtreeUpdate |= properties->clearEffect();
     }
   }
 
   const auto* properties = object.paintProperties();
   if (properties && properties->effect()) {
     context.currentEffect = properties->effect();
     if (!properties->effect()->filter().isEmpty()) {
@@ skipping 470 matching lines @@
 #endif
 
   updateOverflowClip(object, context);
   updatePerspective(object, context);
   updateSvgLocalToBorderBoxTransform(object, context);
   updateScrollAndScrollTranslation(object, context);
   updateOutOfFlowContext(object, context);
 }
 
 }  // namespace blink