mix-blend-mode implementation for accelerated layers

cc/layers/layer_impl.cc

Index: cc/layers/layer_impl.cc
diff --git a/cc/layers/layer_impl.cc b/cc/layers/layer_impl.cc
index 894daf1a27f04cd2b40dfc70436b806af3e59d65..32a8b6021d0f4ea583d8bdad92914216f3bcb923 100644
--- a/cc/layers/layer_impl.cc
+++ b/cc/layers/layer_impl.cc
@@ -51,6 +51,8 @@ LayerImpl::LayerImpl(LayerTreeImpl* tree_impl, int id)
       masks_to_bounds_(false),
       contents_opaque_(false),
       opacity_(1.0),
+      blend_mode_(SkXfermode::kSrcOver_Mode),
+      is_root_for_isolated_group_(false),
       preserves_3d_(false),
       use_parent_backface_visibility_(false),
       draw_checkerboard_for_missing_tiles_(false),
@@ -244,7 +246,8 @@ scoped_ptr<SharedQuadState> LayerImpl::CreateSharedQuadState() const {
                 draw_properties_.visible_content_rect,
                 draw_properties_.clip_rect,
                 draw_properties_.is_clipped,
-                draw_properties_.opacity);
+                draw_properties_.opacity,
+                blend_mode_);
   return state.Pass();
 }
 
@@ -522,6 +525,8 @@ void LayerImpl::PushPropertiesTo(LayerImpl* layer) {
   layer->SetTouchEventHandlerRegion(touch_event_handler_region_);
   layer->SetContentsOpaque(contents_opaque_);
   layer->SetOpacity(opacity_);
+  layer->SetBlendMode(blend_mode_);
+  layer->SetIsRootForIsolatedGroup(is_root_for_isolated_group_);
   layer->SetPosition(position_);
   layer->SetIsContainerForFixedPositionLayers(
       is_container_for_fixed_position_layers_);
@@ -876,6 +881,21 @@ bool LayerImpl::OpacityIsAnimatingOnImplOnly() const {
   return opacity_animation && opacity_animation->is_impl_only();
 }
 
+void LayerImpl::SetBlendMode(SkXfermode::Mode blend_mode) {

[danakj, 2013/11/13 21:02:03]

Can you add these 2 new Set* methods to layer_impl_unittest.cc to verify their
side effects on damage and needs update draw props?

[rosca, 2013/11/14 21:56:34]

Done.

+  if (blend_mode_ == blend_mode)
+    return;
+
+  blend_mode_ = blend_mode;
+  NoteLayerPropertyChangedForSubtree();
+}
+
+void LayerImpl::SetIsRootForIsolatedGroup(bool root) {
+  if (is_root_for_isolated_group_ == root)
+    return;
+
+  is_root_for_isolated_group_ = root;

[danakj, 2013/11/13 21:02:03]

It seems to be this should be causing damage. If this never changes how things
are displayed there'd be no point of it existing, so it must be changing how
things look sometimes.

From discussing with enne@ it sounds like this should be doing
NoteLayerPropertyForSubtree().

[rosca, 2013/11/14 21:56:34]

I think it would be more accurate to call
NoteLayerPropertyChangedForDescendants, because only children may change how
they look due to isolation, not the layer itself. I've changed it, please
correct me if I'm wrong.

[danakj, 2013/11/20 03:32:50]

I'd like enne@ to double check this. I would expect isolation to affect all
layers that draw into the surface equally, not just descendants of the owning
layer? But I don't think I have the same understanding of this part of the CL..

+}
+
 void LayerImpl::SetPosition(gfx::PointF position) {
   if (position_ == position)
     return;
@@ -1277,6 +1297,9 @@ CompositingReasonsAsValue(CompositingReasons reasons) {
   if (reasons & kCompositingReasonOutOfFlowClipping)
     reason_list->AppendString("Has clipping ancestor");
 
+  if (reasons & kCompositingReasonIsolateCompositedDescendants)
+    reason_list->AppendString("Should isolate composited descendants");
+
   return reason_list.PassAs<base::Value>();
 }