Implement GL support for buffer textures

src/gpu/glsl/GrGLSLShaderBuilder.h

Index: src/gpu/glsl/GrGLSLShaderBuilder.h
diff --git a/src/gpu/glsl/GrGLSLShaderBuilder.h b/src/gpu/glsl/GrGLSLShaderBuilder.h
index c408c8ae8446521fdd878385cf5fa8927fce16bb..786ae854e80475d338f5e809d2d984406a0aca6a 100644
--- a/src/gpu/glsl/GrGLSLShaderBuilder.h
+++ b/src/gpu/glsl/GrGLSLShaderBuilder.h
@@ -49,6 +49,17 @@ public:
                                         const char* coordName,
                                         GrSLType coordType = kVec2f_GrSLType);
 
+    void appendTextureLookup(const GrGLSLTextureSampler& sampler, const GrGLSLShaderVar& coord) {
+        this->appendTextureLookup(sampler, coord.getName().c_str(), coord.getType());
+    }
+
+    void appendTextureLookupAndModulate(const char* modulation,
+                                        const GrGLSLTextureSampler& sampler,
+                                        const GrGLSLShaderVar& coord) {
+        this->appendTextureLookupAndModulate(modulation, sampler, coord.getName().c_str(),
+                                             coord.getType());
+    }
+
     /**
     * Adds a #define directive to the top of the shader.
     */
@@ -140,6 +151,7 @@ protected:
         kBlendEquationAdvanced_GLSLPrivateFeature,
         kBlendFuncExtended_GLSLPrivateFeature,
         kExternalTexture_GLSLPrivateFeature,
+        kBufferTexture_GLSLPrivateFeature,
         kFramebufferFetch_GLSLPrivateFeature,
         kNoPerspectiveInterpolation_GLSLPrivateFeature,
         kSampleVariables_GLSLPrivateFeature,