Implement GL support for buffer textures

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 12c1f1fcc6b375e35a677757f28adf76d0a4662a..8ae6219d874ad220d7b3c686690d7abe76547b21 100644
--- a/src/gpu/glsl/GrGLSL.h
+++ b/src/gpu/glsl/GrGLSL.h
@@ -56,9 +56,13 @@ bool GrGLSLSupportsNamedFragmentShaderOutputs(GrGLSLGeneration);
  * Gets the name of the function that should be used to sample a 2D texture. Coord type is used
  * to indicate whether the texture is sampled using projective textured (kVec3f) or not (kVec2f).
  */
-inline const char* GrGLSLTexture2DFunctionName(GrSLType coordType, GrSLType samplerType,
-                                               GrGLSLGeneration glslGen) {
+inline const char* GrGLSLTextureFunctionName(GrSLType coordType, GrSLType samplerType,
+                                             GrGLSLGeneration glslGen) {
     SkASSERT(GrSLTypeIsSamplerType(samplerType));
+    if (kSamplerBuffer_GrSLType == samplerType) {
+        SkASSERT(kInt_GrSLType == coordType);
+        return "texelFetch";
+    }
     SkASSERT(kVec2f_GrSLType == coordType || kVec3f_GrSLType == coordType);
     // GL_TEXTURE_RECTANGLE_ARB is written against OpenGL 2.0/GLSL 1.10. At that time there were
     // separate texture*() functions. In OpenGL 3.0/GLSL 1.30 the different texture*() functions
@@ -110,6 +114,8 @@ static inline const char* GrGLSLTypeString(GrSLType t) {
             return "samplerExternalOES";
         case kSampler2DRect_GrSLType:
             return "sampler2DRect";
+        case kSamplerBuffer_GrSLType:
+            return "samplerBuffer";
         case kBool_GrSLType:
             return "bool";
         case kInt_GrSLType: