Add Texture2D and Sampler GrSLTypes

src/gpu/glsl/GrGLSL.h

Index: src/gpu/glsl/GrGLSL.h
diff --git a/src/gpu/glsl/GrGLSL.h b/src/gpu/glsl/GrGLSL.h
index 844b7c76db9ba65eb067ac487f96a4968a65f419..4d0bb9ae7fc5b6587a38b2e5e2a69745138b1ecf 100644
--- a/src/gpu/glsl/GrGLSL.h
+++ b/src/gpu/glsl/GrGLSL.h
@@ -135,6 +135,10 @@ static inline const char* GrGLSLTypeString(GrSLType t) {
             return "int";
         case kUint_GrSLType:
             return "uint";
+        case kTexture2D_GrSLType:
+            return "texture2D";
+        case kSampler_GrSLType:
+            return "sampler";
         default:
             SkFAIL("Unknown shader var type.");
             return ""; // suppress warning