Add support for IMG's MSAA extension.

src/gpu/gl/GrGLInterface.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/GrGLInterface.h"
 #include "gl/GrGLExtensions.h"
@@ skipping 305 matching lines @@
                 NULL == fBlitFramebuffer) {
                 return false;
             }
         }
         if (extensions.has("GL_APPLE_framebuffer_multisample")) {
             if (NULL == fRenderbufferStorageMultisample ||
                 NULL == fResolveMultisampleFramebuffer) {
                 return false;
             }
         }
+        if (extensions.has("GL_IMG_multisampled_render_to_texture")) {
+            if (NULL == fRenderbufferStorageMultisample ||
+                NULL == fFramebufferTexture2DMultisample) {
+                return false;
+            }
+        }
     }
 
     // On ES buffer mapping is an extension. On Desktop
     // buffer mapping was part of original VBO extension
     // which we require.
     if (kDesktop_GrGLBinding == binding || extensions.has("GL_OES_mapbuffer")) {
         if (NULL == fMapBuffer ||
             NULL == fUnmapBuffer) {
             return false;
         }
@@ skipping 26 matching lines @@
             if (NULL == fBindVertexArray ||
                 NULL == fDeleteVertexArrays ||
                 NULL == fGenVertexArrays) {
                 return false;
             }
         }
     }
 
     return true;
 }