Add swapBuffer call to SkGLContextHelper.

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 86 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.");
         }
     }
 }
+
+void SkMesaGLContext::swapBuffers() const { }