Add glReadBuffer to GrGLInterface.

Review URL: http://codereview.appspot.com/4841048/





git-svn-id: http://skia.googlecode.com/svn/trunk@2034 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gpu/src/mesa/GrGLDefaultInterface_mesa.cpp b/gpu/src/mesa/GrGLDefaultInterface_mesa.cpp
index 56f2cf7..c6be2df 100644
--- a/gpu/src/mesa/GrGLDefaultInterface_mesa.cpp
+++ b/gpu/src/mesa/GrGLDefaultInterface_mesa.cpp
@@ -91,6 +91,7 @@
         gDefaultInterface.fMatrixMode = glMatrixMode;
         gDefaultInterface.fPointSize = glPointSize;
         gDefaultInterface.fPixelStorei = glPixelStorei;
+        gDefaultInterface.fReadBuffer = glReadBuffer;
         gDefaultInterface.fReadPixels = glReadPixels;
         gDefaultInterface.fScissor = glScissor;
         gDefaultInterface.fShadeModel = glShadeModel;