Fix alpha textures in NV ES3 contexts on Windows

src/gpu/gl/GrGLUtil.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrGLUtil_DEFINED
 #define GrGLUtil_DEFINED
 
@@ skipping 16 matching lines @@
 #define GR_GLSL_INVALID_VER GR_GL_VER(0, 0)
 
 /**
  * The Vendor and Renderer enum values are lazily updated as required.
  */
 enum GrGLVendor {
     kARM_GrGLVendor,
     kImagination_GrGLVendor,
     kIntel_GrGLVendor,
     kQualcomm_GrGLVendor,
+    kNVIDIA_GrGLVendor,
 
     kOther_GrGLVendor
 };
 
 enum GrGLRenderer {
     kTegra2_GrGLRenderer,
     kTegra3_GrGLRenderer,
 
     kOther_GrGLRenderer
 };
@@ skipping 127 matching lines @@
     do {                                                        \
         GR_GL_CALLBACK_IMPL(IFACE);                             \
         (RET) = (IFACE)->fFunctions.f##X;                       \
         GR_GL_LOG_CALLS_IMPL(X);                                \
     } while (false)
 
 // call glGetError without doing a redundant error check or logging.
 #define GR_GL_GET_ERROR(IFACE) (IFACE)->fFunctions.fGetError()
 
 #endif