[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 de0780d784073d9cce445369085f811402ca5ae7..e03e4794b5f0c7b4cbaa136f4e4b2608bc034310 100644
--- a/Source/core/rendering/RenderLayerCompositor.cpp
+++ b/Source/core/rendering/RenderLayerCompositor.cpp
@@ -1658,7 +1658,6 @@ bool RenderLayerCompositor::requiresOwnBackingStore(const RenderLayer* layer, co
         || requiresCompositingForAnimation(renderer)
         || requiresCompositingForTransition(renderer)
         || requiresCompositingForFilters(renderer)
-        || requiresCompositingForBlending(renderer)
         || requiresCompositingForPosition(renderer, layer)
         || requiresCompositingForOverflowScrolling(layer)
         || requiresCompositingForOverflowScrollingParent(layer)
@@ -1717,9 +1716,6 @@ CompositingReasons RenderLayerCompositor::directReasonsForCompositing(const Rend
     if (requiresCompositingForOverflowScrolling(layer))
         directReasons |= CompositingReasonOverflowScrollingTouch;
 
-    if (requiresCompositingForBlending(renderer))
-        directReasons |= CompositingReasonBlending;
-
     if (requiresCompositingForOverflowScrollingParent(layer))
         directReasons |= CompositingReasonOverflowScrollingParent;
 
@@ -2048,11 +2044,6 @@ bool RenderLayerCompositor::requiresCompositingForFilters(RenderObject* renderer
     return renderer->hasFilter();
 }
 
-bool RenderLayerCompositor::requiresCompositingForBlending(RenderObject* renderer) const
-{
-    return renderer->hasBlendMode();
-}
-
 bool RenderLayerCompositor::requiresCompositingForOverflowScrollingParent(const RenderLayer* layer) const
 {
     return !!layer->scrollParent();