added support for glMinSampleShading

src/gpu/gl/GrGLInterface.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "gl/GrGLInterface.h"
 #include "gl/GrGLExtensions.h"
@@ skipping 763 matching lines @@
             nullptr == fFunctions.fDebugMessageInsert ||
             nullptr == fFunctions.fDebugMessageCallback ||
             nullptr == fFunctions.fGetDebugMessageLog ||
             nullptr == fFunctions.fPushDebugGroup ||
             nullptr == fFunctions.fPopDebugGroup ||
             nullptr == fFunctions.fObjectLabel) {
             RETURN_FALSE_INTERFACE
         }
     }
 
+    if ((kGL_GrGLStandard == fStandard && glVer >= GR_GL_VER(4,0)) ||
+        fExtensions.has("GL_ARB_sample_shading")) {
+        if (nullptr == fFunctions.fMinSampleShading) {
+            RETURN_FALSE_INTERFACE
+        }
+    } else if (kGL_GrGLStandard == fStandard && fExtensions.has("GL_OES_sample_shading")) {
+        if (nullptr == fFunctions.fMinSampleShading) {
+            RETURN_FALSE_INTERFACE
+        }
+    }
+
     if (fExtensions.has("EGL_KHR_image") || fExtensions.has("EGL_KHR_image_base")) {
         if (nullptr == fFunctions.fEGLCreateImage ||
             nullptr == fFunctions.fEGLDestroyImage) {
             RETURN_FALSE_INTERFACE
         }
     }
 
     return true;
 }