[CSS Blending] Implement mix-blend-mode in software.

Source/core/rendering/RenderLayerCompositor.cpp

Index: Source/core/rendering/RenderLayerCompositor.cpp
diff --git a/Source/core/rendering/RenderLayerCompositor.cpp b/Source/core/rendering/RenderLayerCompositor.cpp
index e7b5a0f21a3d37333f34d10368c69e0914d43ea4..8c6aeb9669b8eb44a25c3d2c29edeaa808dce4ad 100644
--- a/Source/core/rendering/RenderLayerCompositor.cpp
+++ b/Source/core/rendering/RenderLayerCompositor.cpp
@@ -1586,7 +1586,6 @@ bool RenderLayerCompositor::requiresOwnBackingStore(const RenderLayer* layer, co
         || requiresCompositingForAnimation(renderer)
         || requiresCompositingForTransition(renderer)
         || requiresCompositingForFilters(renderer)
-        || requiresCompositingForBlending(renderer)
         || requiresCompositingForPosition(renderer, layer)
         || requiresCompositingForOverflowScrolling(layer)
         || requiresCompositingForOverflowScrollingParent(layer)
@@ -1645,9 +1644,6 @@ CompositingReasons RenderLayerCompositor::directReasonsForCompositing(const Rend
     if (requiresCompositingForOverflowScrolling(layer))
         directReasons |= CompositingReasonOverflowScrollingTouch;
 
-    if (requiresCompositingForBlending(renderer))
-        directReasons |= CompositingReasonBlending;
-
     if (requiresCompositingForOverflowScrollingParent(layer))
         directReasons |= CompositingReasonOverflowScrollingParent;
 
@@ -1970,11 +1966,6 @@ bool RenderLayerCompositor::requiresCompositingForFilters(RenderObject* renderer
     return renderer->hasFilter();
 }
 
-bool RenderLayerCompositor::requiresCompositingForBlending(RenderObject* renderer) const
-{
-    return renderer->hasBlendMode();
-}
-
 bool RenderLayerCompositor::requiresCompositingForOverflowScrollingParent(const RenderLayer* layer) const
 {
     if (!layer->compositorDrivenAcceleratedScrollingEnabled())