Fix GrGLInterface::validate() to check for GL_OES_sample_shading on ES contexts
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2156343004

Review-Url: https://codereview.chromium.org/2156343004
diff --git a/src/gpu/gl/GrGLInterface.cpp b/src/gpu/gl/GrGLInterface.cpp
index 949e2bf..d11a86b 100644
--- a/src/gpu/gl/GrGLInterface.cpp
+++ b/src/gpu/gl/GrGLInterface.cpp
@@ -774,7 +774,7 @@
         if (nullptr == fFunctions.fMinSampleShading) {
             RETURN_FALSE_INTERFACE
         }
-    } else if (kGL_GrGLStandard == fStandard && fExtensions.has("GL_OES_sample_shading")) {
+    } else if (kGLES_GrGLStandard == fStandard && fExtensions.has("GL_OES_sample_shading")) {
         if (nullptr == fFunctions.fMinSampleShading) {
             RETURN_FALSE_INTERFACE
         }