Implement GL support for buffer textures

src/gpu/gl/GrGLTexture.cpp

Index: src/gpu/gl/GrGLTexture.cpp
diff --git a/src/gpu/gl/GrGLTexture.cpp b/src/gpu/gl/GrGLTexture.cpp
index aff91ebe223fb113ca5e986f45cb50e96b952494..43272ff852ec302cbcdfec40bb9556931677264a 100644
--- a/src/gpu/gl/GrGLTexture.cpp
+++ b/src/gpu/gl/GrGLTexture.cpp
@@ -19,6 +19,8 @@ inline static GrSLType sampler_type(const GrGLTexture::IDDesc& idDesc, const GrG
     } else if (idDesc.fInfo.fTarget == GR_GL_TEXTURE_RECTANGLE) {
         SkASSERT(gpu->glCaps().rectangleTextureSupport());
         return kSampler2DRect_GrSLType;
+    } else if (GR_GL_TEXTURE_BUFFER == idDesc.fInfo.fTarget) {
+        return kSamplerBuffer_GrSLType;
     } else {
         SkASSERT(idDesc.fInfo.fTarget == GR_GL_TEXTURE_2D);
         return kSampler2D_GrSLType;