Add clone to Stage. Rename place to mix and PolymorphicUnion to Stage. Cleanup.

src/core/SkLinearBitmapPipeline.h

Index: src/core/SkLinearBitmapPipeline.h
diff --git a/src/core/SkLinearBitmapPipeline.h b/src/core/SkLinearBitmapPipeline.h
index 32e464100fc2144696193d77a5547ece56befd02..548302ef9acdade777548960e62dc9d35035e538 100644
--- a/src/core/SkLinearBitmapPipeline.h
+++ b/src/core/SkLinearBitmapPipeline.h
@@ -8,11 +8,9 @@
 #ifndef SkLinearBitmapPipeline_DEFINED
 #define SkLinearBitmapPipeline_DEFINED
 
-
 #include "SkColor.h"
 #include "SkImageInfo.h"
 #include "SkMatrix.h"
-#include "SkNx.h"
 #include "SkShader.h"
 
 class SkLinearBitmapPipeline {
@@ -27,31 +25,33 @@ public:
 
     void shadeSpan4f(int x, int y, SkPM4f* dst, int count);
 
-    template<typename Base, size_t kSize>
-    class PolymorphicUnion {
+    template<typename Base, size_t kSize, typename Next = void>
+    class Stage {
     public:
-        PolymorphicUnion() : fIsInitialized{false} {}
+        Stage() : fIsInitialized{false} {}
+        ~Stage();
 
-        ~PolymorphicUnion() {
-            if (fIsInitialized) {
-                this->get()->~Base();
-            }
-        }
+        template<typename Variant, typename... Args>
+        void initStage(Next* next, Args&& ... args);
 
         template<typename Variant, typename... Args>
-        void Initialize(Args&&... args) {
-            SkASSERTF(sizeof(Variant) <= sizeof(fSpace),
-                      "Size Variant: %d, Space: %d", sizeof(Variant), sizeof(fSpace));
+        void initSink(Args&& ... args);
 
-            new(&fSpace) Variant(std::forward<Args>(args)...);
-            fIsInitialized = true;
-        };
+        template <typename To, typename From>
+        To* getInterface();
+
+        // Copy this stage to `cloneToStage` with `next` as its next stage
+        // (not necessarily the same as our next, you see), returning `cloneToStage`.
+        // Note: There is no cloneSinkTo method because the code usually places the top part of
+        // the pipeline on a new sampler.
+        Base* cloneStageTo(Next* next, Stage* cloneToStage) const;
 
         Base* get() const { return reinterpret_cast<Base*>(&fSpace); }
         Base* operator->() const { return this->get(); }
         Base& operator*() const { return *(this->get()); }
 
     private:
+        std::function<void (Next*, void*)> fStageCloner;
         struct SK_STRUCT_ALIGN(16) Space {
             char space[kSize];
         };
@@ -61,22 +61,22 @@ public:
 
     class PointProcessorInterface;
     class SampleProcessorInterface;
-    class PixelPlacerInterface;
+    class BlendProcessorInterface;
     class DestinationInterface;
 
-    // These values were generated by the assert above in PolymorphicUnion.
-    using MatrixStage = PolymorphicUnion<PointProcessorInterface, 160>;
-    using TileStage   = PolymorphicUnion<PointProcessorInterface, 160>;
-    using SampleStage = PolymorphicUnion<SampleProcessorInterface,100>;
-    using PixelStage  = PolymorphicUnion<PixelPlacerInterface,     80>;
+    // These values were generated by the assert above in Stage::init{Sink|Stage}.
+    using MatrixStage  = Stage<PointProcessorInterface, 160, PointProcessorInterface>;
+    using TileStage    = Stage<PointProcessorInterface, 160, SampleProcessorInterface>;
+    using SampleStage  = Stage<SampleProcessorInterface, 100, BlendProcessorInterface>;
+    using BlenderStage = Stage<BlendProcessorInterface, 80>;
 
 private:
     PointProcessorInterface* fFirstStage;
-    MatrixStage fMatrixStage;
-    TileStage   fTiler;
-    SampleStage fSampleStage;
-    PixelStage  fPixelStage;
-    DestinationInterface* fLastStage;
+    MatrixStage              fMatrixStage;
+    TileStage                fTileStage;
+    SampleStage              fSampleStage;
+    BlenderStage             fBlenderStage;
+    DestinationInterface*    fLastStage;
 };
 
 #endif  // SkLinearBitmapPipeline_DEFINED