Refactor how we store and use samplers in Ganesh

src/gpu/glsl/GrGLSLUniformHandler.h

Index: src/gpu/glsl/GrGLSLUniformHandler.h
diff --git a/src/gpu/glsl/GrGLSLUniformHandler.h b/src/gpu/glsl/GrGLSLUniformHandler.h
index a2f70532adc2948de8641b18b632a727a026e844..56cac4a49fe26e004bf8cda9384469dfb4f6c0ce 100644
--- a/src/gpu/glsl/GrGLSLUniformHandler.h
+++ b/src/gpu/glsl/GrGLSLUniformHandler.h
@@ -12,12 +12,14 @@
 #include "GrGLSLShaderVar.h"
 
 class GrGLSLProgramBuilder;
+class GrGLSLSampler;
 
 class GrGLSLUniformHandler {
 public:
     virtual ~GrGLSLUniformHandler() {}
 
     typedef GrGLSLProgramDataManager::UniformHandle UniformHandle;
+    typedef GrGLSLProgramDataManager::UniformHandle SamplerHandle;
 
     /** Add a uniform variable to the current program, that has visibility in one or more shaders.
         visibility is a bitfield of GrShaderFlag values indicating from which shaders the uniform
@@ -30,6 +32,7 @@ public:
                              GrSLPrecision precision,
                              const char* name,
                              const char** outName = nullptr) {
+        SkASSERT(!GrSLTypeIsSamplerType(type));
         return this->addUniformArray(visibility, type, precision, name, 0, outName);
     }
 
@@ -39,6 +42,7 @@ public:
                                   const char* name,
                                   int arrayCount,
                                   const char** outName = nullptr) {
+        SkASSERT(!GrSLTypeIsSamplerType(type));
         return this->internalAddUniformArray(visibility, type, precision, name, true, arrayCount,
                                              outName);
     }
@@ -49,6 +53,7 @@ public:
      * Shortcut for getUniformVariable(u).c_str()
      */
     virtual const char* getUniformCStr(UniformHandle u) const = 0;
+
 protected:
     explicit GrGLSLUniformHandler(GrGLSLProgramBuilder* program) : fProgramBuilder(program) {}
 
@@ -56,6 +61,23 @@ protected:
     GrGLSLProgramBuilder* fProgramBuilder;
 
 private:
+    virtual int numSamplers() const = 0;
+    virtual const GrGLSLSampler& getSampler(SamplerHandle handle) const = 0;
+
+    SamplerHandle addSampler(uint32_t visibility,
+                             GrPixelConfig config,
+                             GrSLType type,
+                             GrSLPrecision precision,
+                             const char* name) {
+        return this->internalAddSampler(visibility, config, type, precision, name);
+    }
+
+    virtual SamplerHandle internalAddSampler(uint32_t visibility,
+                                             GrPixelConfig config,
+                                             GrSLType type,
+                                             GrSLPrecision precision,
+                                             const char* name) = 0;
+
     virtual UniformHandle internalAddUniformArray(uint32_t visibility,
                                                   GrSLType type,
                                                   GrSLPrecision precision,