[cc] Add SkBlendMode::kDstIn support to cc::Layer

cc/layers/layer.cc

 // Copyright 2010 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 "cc/layers/layer.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 483 matching lines @@
 
 bool Layer::AlwaysUseActiveTreeOpacity() const {
   return false;
 }
 
 void Layer::SetBlendMode(SkBlendMode blend_mode) {
   DCHECK(IsPropertyChangeAllowed());
   if (inputs_.blend_mode == blend_mode)
     return;
 
-  // Allowing only blend modes that are defined in the CSS Compositing standard:
+  // Allowing only blend modes that are defined in the CSS Compositing standard,
+  // plus destination-in which is used to implement masks.
   // http://dev.w3.org/fxtf/compositing-1/#blending
   switch (blend_mode) {
     case SkBlendMode::kSrcOver:
+    case SkBlendMode::kDstIn:
     case SkBlendMode::kScreen:
     case SkBlendMode::kOverlay:
     case SkBlendMode::kDarken:
     case SkBlendMode::kLighten:
     case SkBlendMode::kColorDodge:
     case SkBlendMode::kColorBurn:
     case SkBlendMode::kHardLight:
     case SkBlendMode::kSoftLight:
     case SkBlendMode::kDifference:
     case SkBlendMode::kExclusion:
     case SkBlendMode::kMultiply:
     case SkBlendMode::kHue:
     case SkBlendMode::kSaturation:
     case SkBlendMode::kColor:
     case SkBlendMode::kLuminosity:
       // supported blend modes
       break;
     case SkBlendMode::kClear:
     case SkBlendMode::kSrc:
     case SkBlendMode::kDst:
     case SkBlendMode::kDstOver:
     case SkBlendMode::kSrcIn:
-    case SkBlendMode::kDstIn:
     case SkBlendMode::kSrcOut:
     case SkBlendMode::kDstOut:
     case SkBlendMode::kSrcATop:
     case SkBlendMode::kDstATop:
     case SkBlendMode::kXor:
     case SkBlendMode::kPlus:
     case SkBlendMode::kModulate:
       // Porter Duff Compositing Operators are not yet supported
       // http://dev.w3.org/fxtf/compositing-1/#porterduffcompositingoperators
       NOTREACHED();
@@ skipping 1037 matching lines @@
   DCHECK_NE(transform_tree_index_, TransformTree::kInvalidNodeId);
   return draw_property_utils::ScreenSpaceTransform(
       this, layer_tree_->property_trees()->transform_tree);
 }
 
 LayerTree* Layer::GetLayerTree() const {
   return layer_tree_;
 }
 
 }  // namespace cc