Refactor how we store and use samplers in Ganesh

src/gpu/vk/GrVkGLSLSampler.h

+/*
+* Copyright 2016 Google Inc.
+*
+* Use of this source code is governed by a BSD-style license that can be
+* found in the LICENSE file.
+*/
+
+#ifndef GrVkGLSLSampler_DEFINED
+#define GrVkGLSLSampler_DEFINED
+
+#include "glsl/GrGLSLSampler.h"
+
+#include "glsl/GrGLSLShaderVar.h"
+
+class GrVkGLSLSampler : public GrGLSLSampler {
+public:
+    GrVkGLSLSampler(uint32_t visibility,
+                    GrPixelConfig config,
+                    GrSLType type,
+                    GrSLPrecision precision,
+                    const char* name,
+                    uint32_t binding,
+                    uint32_t set) : INHERITED(visibility, config), fBinding(binding) {
+        SkASSERT(GrSLTypeIsSamplerType(type));
+        fShaderVar.setType(type);
+        fShaderVar.setTypeModifier(GrGLSLShaderVar::kUniform_TypeModifier);
+        fShaderVar.setPrecision(precision);
+        fShaderVar.accessName()->set(name);
+        SkString layoutQualifier;
+        layoutQualifier.appendf("set=%d, binding=%d", set, binding);
+        fShaderVar.setLayoutQualifier(layoutQualifier.c_str());
+    }
+
+    GrSLType type() const override { return fShaderVar.getType(); }
+    uint32_t binding() const { return fBinding; }
+
+    const char* onGetSamplerNameForTexture2D() const override { return fShaderVar.c_str(); }
+    const char* getSamplerNameForTexelFetch() const override { return fShaderVar.c_str(); }
+
+private:
+    GrGLSLShaderVar fShaderVar;
+    uint32_t        fBinding;
+
+    friend class GrVkUniformHandler;
+
+    typedef GrGLSLSampler INHERITED;
+};
+
+#endif