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

src/gpu/gl/GrGLSL.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrGLSL.h"
 #include "GrGLShaderVar.h"
 #include "SkString.h"
 
-GrGLSLGeneration GrGetGLSLGeneration(const GrGLInterface* gl) {
+bool GrGetGLSLGeneration(const GrGLInterface* gl, GrGLSLGeneration* generation) {
+    SkASSERT(NULL != generation);
     GrGLSLVersion ver = GrGLGetGLSLVersion(gl);
+    if (GR_GLSL_INVALID_VER == ver) {
+        return false;
+    }
     switch (gl->fStandard) {
         case kGL_GrGLStandard:
             SkASSERT(ver >= GR_GLSL_VER(1,10));
             if (ver >= GR_GLSL_VER(1,50)) {
-                return k150_GrGLSLGeneration;
+                *generation = k150_GrGLSLGeneration;
             } else if (ver >= GR_GLSL_VER(1,40)) {
-                return k140_GrGLSLGeneration;
+                *generation = k140_GrGLSLGeneration;
             } else if (ver >= GR_GLSL_VER(1,30)) {
-                return k130_GrGLSLGeneration;
+                *generation = k130_GrGLSLGeneration;
             } else {
-                return k110_GrGLSLGeneration;
+                *generation = k110_GrGLSLGeneration;
             }
+            return true;
         case kGLES_GrGLStandard:
             // version 1.00 of ES GLSL based on ver 1.20 of desktop GLSL
             SkASSERT(ver >= GR_GL_VER(1,00));
-            return k110_GrGLSLGeneration;
+            *generation = k110_GrGLSLGeneration;
+            return true;
         default:
             GrCrash("Unknown GL Standard");
-            return k110_GrGLSLGeneration; // suppress warning
+            return false;
     }
 }
 
 const char* GrGetGLSLVersionDecl(const GrGLContextInfo& info) {
     switch (info.glslGeneration()) {
         case k110_GrGLSLGeneration:
             if (kGLES_GrGLStandard == info.standard()) {
                 // ES2s shader language is based on version 1.20 but is version
                 // 1.00 of the ES language.
                 return "#version 100\n";
@@ skipping 40 matching lines @@
     }
 
     append_tabs(outAppend, tabCnt);
 
     if (mulFactor.isZeros()) {
         outAppend->appendf("%s = vec4(0);\n", vec4VarName);
     } else {
         outAppend->appendf("%s *= %s;\n", vec4VarName, mulFactor.c_str());
     }
 }