Adds support for OES_mapbuffer

BUG=angle:581

Change-Id: I05824051789a77c8169ec5830731e6155c507fc4
Reviewed-on: https://chromium-review.googlesource.com/191650
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Shannon Woods <shannonwoods@chromium.org>
diff --git a/src/libGLESv2/validationES.cpp b/src/libGLESv2/validationES.cpp
index 741770b..9001561 100644
--- a/src/libGLESv2/validationES.cpp
+++ b/src/libGLESv2/validationES.cpp
@@ -106,10 +106,10 @@
       case GL_ELEMENT_ARRAY_BUFFER:
         return true;
 
-      case GL_COPY_READ_BUFFER:
-      case GL_COPY_WRITE_BUFFER:
       case GL_PIXEL_PACK_BUFFER:
       case GL_PIXEL_UNPACK_BUFFER:
+      case GL_COPY_READ_BUFFER:
+      case GL_COPY_WRITE_BUFFER:
       case GL_TRANSFORM_FEEDBACK_BUFFER:
       case GL_UNIFORM_BUFFER:
         return (context->getClientVersion() >= 3);