Fix mesa issues.

src/gpu/gl/mesa/SkMesaGLContext.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 <GL/osmesa.h>
 
@@ skipping 24 matching lines @@
     GR_STATIC_ASSERT(sizeof(Context) == sizeof(OSMesaContext));
 }
 
 SkMesaGLContext::~SkMesaGLContext() {
     this->destroyGLContext();
 }
 
 void SkMesaGLContext::destroyGLContext() {
     if (fImage) {
         sk_free(fImage);
+        fImage = NULL;
     }
 
     if (fContext) {
         OSMesaDestroyContext((OSMesaContext)fContext);
+        fContext = static_cast<Context>(NULL);
     }
 }
 
 static const GrGLint gBOGUS_SIZE = 16;
 
 const GrGLInterface* SkMesaGLContext::createGLContext() {
     /* Create an RGBA-mode context */
 #if OSMESA_MAJOR_VERSION * 100 + OSMESA_MINOR_VERSION >= 305
     /* specify Z, stencil, accum sizes */
     fContext = (Context)OSMesaCreateContextExt(OSMESA_BGRA, 0, 0, 0, NULL);
@@ skipping 36 matching lines @@
 }
 
 void SkMesaGLContext::makeCurrent() const {
     if (fContext) {
         if (!OSMesaMakeCurrent((OSMesaContext)fContext, fImage,
                                GR_GL_UNSIGNED_BYTE, gBOGUS_SIZE, gBOGUS_SIZE)) {
             SkDebugf("Could not make MESA context current.");
         }
     }
 }