Move the matrix stage of SkLinearBitmapPipeline over to using SkSmallAllocator.

src/core/SkLinearBitmapPipeline.h

Index: src/core/SkLinearBitmapPipeline.h
diff --git a/src/core/SkLinearBitmapPipeline.h b/src/core/SkLinearBitmapPipeline.h
index 776f8d86039ca65e9d1629bcc03d1d69da025f69..ed621a9454f5665157c9727c68999f98f622c56e 100644
--- a/src/core/SkLinearBitmapPipeline.h
+++ b/src/core/SkLinearBitmapPipeline.h
@@ -12,6 +12,7 @@
 #include "SkImageInfo.h"
 #include "SkMatrix.h"
 #include "SkShader.h"
+#include "SkSmallAllocator.h"
 
 class SkEmbeddableLinearPipeline;
 
@@ -125,15 +126,23 @@ public:
     class PixelAccessorInterface;
 
     // These values were generated by the assert above in Stage::init{Sink|Stage}.
-    using MatrixStage  = Stage<PointProcessorInterface,     56, PointProcessorInterface>;
     using TileStage    = Stage<PointProcessorInterface,     48, SampleProcessorInterface>;
     using SampleStage  = Stage<SampleProcessorInterface,   160, BlendProcessorInterface>;
     using BlenderStage = Stage<BlendProcessorInterface,     48>;
     using Accessor     = PolyMemory<PixelAccessorInterface, 64>;
 
 private:
+    PointProcessorInterface* ChooseMatrix(
+        PointProcessorInterface* next,
+        const SkMatrix& inverse);
+
+    using MemoryAllocator = SkSmallAllocator<64, 1>;
+    using MatrixCloner =
+        std::function<PointProcessorInterface* (PointProcessorInterface*, MemoryAllocator*)>;
+
+    MemoryAllocator          fMemory;
     PointProcessorInterface* fFirstStage;
-    MatrixStage              fMatrixStage;
+    MatrixCloner             fMatrixStageCloner;
     TileStage                fTileStage;
     SampleStage              fSampleStage;
     BlenderStage             fBlenderStage;