Fail to create GrContext when we get a NULL for a GL/GLSL version string

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
 
 #include "gl/GrGLInterface.h"
 #include "GrGLDefines.h"
 
 class SkMatrix;
 
 ////////////////////////////////////////////////////////////////////////////////
 
 typedef uint32_t GrGLVersion;
 typedef uint32_t GrGLSLVersion;
 
+#define GR_GL_VER(major, minor) ((static_cast<int>(major) << 16) | \
+                                 static_cast<int>(minor))
+#define GR_GLSL_VER(major, minor) ((static_cast<int>(major) << 16) | \
+                                   static_cast<int>(minor))
+
+#define GR_GL_INVALID_VER GR_GL_VER(0, 0)
+#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,
 
     kOther_GrGLVendor
 };
 
 enum GrGLRenderer {
     kTegra2_GrGLRenderer,
     kTegra3_GrGLRenderer,
 
     kOther_GrGLRenderer
 };
 
-#define GR_GL_VER(major, minor) ((static_cast<int>(major) << 16) | \
-                                 static_cast<int>(minor))
-#define GR_GLSL_VER(major, minor) ((static_cast<int>(major) << 16) | \
-                                   static_cast<int>(minor))
-
 ////////////////////////////////////////////////////////////////////////////////
 
 /**
  *  Some drivers want the var-int arg to be zero-initialized on input.
  */
 #define GR_GL_INIT_ZERO     0
 #define GR_GL_GetIntegerv(gl, e, p)                                            \
     do {                                                                       \
         *(p) = GR_GL_INIT_ZERO;                                                \
         GR_GL_CALL(gl, GetIntegerv(e, p));                                     \
@@ skipping 116 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