Plumbed in discard_framebuffer extension

https://codereview.chromium.org/14461006/



git-svn-id: http://skia.googlecode.com/svn/trunk@8906 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/gl/GrGLCreateNullInterface.cpp b/src/gpu/gl/GrGLCreateNullInterface.cpp
index 5a5ec6b..1c2e1cd 100644
--- a/src/gpu/gl/GrGLCreateNullInterface.cpp
+++ b/src/gpu/gl/GrGLCreateNullInterface.cpp
@@ -241,6 +241,7 @@
         interface->fTexParameteriv = noOpGLTexParameteriv;
         interface->fTexSubImage2D = noOpGLTexSubImage2D;
         interface->fTexStorage2D = noOpGLTexStorage2D;
+        interface->fDiscardFramebuffer = noOpGLDiscardFramebuffer;
         interface->fUniform1f = noOpGLUniform1f;
         interface->fUniform1i = noOpGLUniform1i;
         interface->fUniform1fv = noOpGLUniform1fv;