Adding blend mode to DrawProperties

cc/layers/draw_properties.h

 // Copyright 2012 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.
 
 #ifndef CC_LAYERS_DRAW_PROPERTIES_H_
 #define CC_LAYERS_DRAW_PROPERTIES_H_
 
 #include "base/memory/scoped_ptr.h"
+#include "third_party/skia/include/core/SkXfermode.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/transform.h"
 
 namespace cc {
 
 // Container for properties that layers need to compute before they can be
 // drawn.
 template <typename LayerType>
 struct CC_EXPORT DrawProperties {
   DrawProperties()
       : opacity(0.f),
         opacity_is_animating(false),
+        blend_mode(SkXfermode::kSrcOver_Mode),
         screen_space_opacity_is_animating(false),
         target_space_transform_is_animating(false),
         screen_space_transform_is_animating(false),
         can_use_lcd_text(false),
         is_clipped(false),
         render_target(NULL),
         contents_scale_x(1.f),
         contents_scale_y(1.f),
         num_unclipped_descendants(0),
         layer_or_descendant_has_copy_request(false),
@@ skipping 20 matching lines @@
   // DrawProperties::opacity may be different than LayerType::opacity,
   // particularly in the case when a RenderSurface re-parents the layer's
   // opacity, or when opacity is compounded by the hierarchy.
   float opacity;
 
   // xxx_is_animating flags are used to indicate whether the DrawProperties
   // are actually meaningful on the main thread. When the properties are
   // animating, the main thread may not have the same values that are used
   // to draw.
   bool opacity_is_animating;
+
+  // DrawProperties::blend_mode may be different than LayerType::blend_mode,
+  // particularly in the case when the LayerType has it own RenderSurface which
+  // will take the responsibility to blend the entire subtree.
+  SkXfermode::Mode blend_mode;
+
   bool screen_space_opacity_is_animating;
   bool target_space_transform_is_animating;
   bool screen_space_transform_is_animating;
 
   // True if the layer can use LCD text.
   bool can_use_lcd_text;
 
   // True if the layer needs to be clipped by clip_rect.
   bool is_clipped;
 
@@ skipping 74 matching lines @@
   // have page scale applied and others not, this may differ between layers.
   float page_scale_factor;
 
   // The device scale factor that is applied to the layer.
   float device_scale_factor;
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_DRAW_PROPERTIES_H_