added support for glMinSampleShading

src/gpu/gl/GrGLAssembleInterface.cpp

Index: src/gpu/gl/GrGLAssembleInterface.cpp
diff --git a/src/gpu/gl/GrGLAssembleInterface.cpp b/src/gpu/gl/GrGLAssembleInterface.cpp
index 6672d224fdb5325c4c0ff9dbbabe198f70785a4c..d1b2fb63fb675366e1a9687ce803ea4f16334a0d 100644
--- a/src/gpu/gl/GrGLAssembleInterface.cpp
+++ b/src/gpu/gl/GrGLAssembleInterface.cpp
@@ -515,6 +515,10 @@ const GrGLInterface* GrGLAssembleGLInterface(void* ctx, GrGLGetProc get) {
         GET_EGL_PROC_SUFFIX(DestroyImage, KHR);
     }
 
+    if (glVer >= GR_GL_VER(4,0) || extensions.has("GL_ARB_sample_shading")) {
+        GET_PROC(MinSampleShading);
+    }
+
     interface->fStandard = kGL_GrGLStandard;
     interface->fExtensions.swap(&extensions);
 
@@ -893,6 +897,10 @@ const GrGLInterface* GrGLAssembleGLESInterface(void* ctx, GrGLGetProc get) {
         GET_EGL_PROC_SUFFIX(DestroyImage, KHR);
     }
 
+    if (extensions.has("GL_OES_sample_shading")) {
+        GET_PROC_SUFFIX(MinSampleShading, OES);
+    }
+
     interface->fStandard = kGLES_GrGLStandard;
     interface->fExtensions.swap(&extensions);