Fix alpha textures in NV ES3 contexts on Windows

src/gpu/gl/GrGLUtil.cpp

Index: src/gpu/gl/GrGLUtil.cpp
diff --git a/src/gpu/gl/GrGLUtil.cpp b/src/gpu/gl/GrGLUtil.cpp
index 0fa2d2ce1882289f450ee3297727fbfdecf0dc5f..6a2eb6e17ee0e62c94723e859cbc78ad8d7ef3e9 100644
--- a/src/gpu/gl/GrGLUtil.cpp
+++ b/src/gpu/gl/GrGLUtil.cpp
@@ -219,6 +219,9 @@ GrGLVendor GrGLGetVendorFromString(const char* vendorString) {
         if (0 == strcmp(vendorString, "Qualcomm")) {
             return kQualcomm_GrGLVendor;
         }
+        if (0 == strcmp(vendorString, "NVIDIA Corporation")) {
+                return kNVIDIA_GrGLVendor;
+        }
     }
     return kOther_GrGLVendor;
 }