Add a cache of GrVkSamplers in GrVkResourceProvider.

src/gpu/vk/GrVkProgram.h

Index: src/gpu/vk/GrVkProgram.h
diff --git a/src/gpu/vk/GrVkProgram.h b/src/gpu/vk/GrVkProgram.h
index e0477260e98637cca94b559f40a910691b8c915a..9b4eeb1e93089ad8c0e2007a6b03e85f3f1df0da 100644
--- a/src/gpu/vk/GrVkProgram.h
+++ b/src/gpu/vk/GrVkProgram.h
@@ -33,7 +33,7 @@ public:
 
     GrVkPipeline* vkPipeline() const { return fPipeline; }
 
-    void setData(const GrVkGpu*, const GrPrimitiveProcessor&, const GrPipeline&);
+    void setData(GrVkGpu*, const GrPrimitiveProcessor&, const GrPipeline&);
 
     void bind(const GrVkGpu* gpu, GrVkCommandBuffer* commandBuffer);
 
@@ -68,7 +68,7 @@ private:
 
     void writeUniformBuffers(const GrVkGpu* gpu);
 
-    void writeSamplers(const GrVkGpu* gpu, const SkTArray<const GrTextureAccess*>& textureBindings);
+    void writeSamplers(GrVkGpu* gpu, const SkTArray<const GrTextureAccess*>& textureBindings);
 
 
     /**