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/renderer/d3d11/Renderer11.cpp b/src/libGLESv2/renderer/d3d11/Renderer11.cpp
index 3df4834..ba56a0c 100644
--- a/src/libGLESv2/renderer/d3d11/Renderer11.cpp
+++ b/src/libGLESv2/renderer/d3d11/Renderer11.cpp
@@ -2013,6 +2013,11 @@
     return true;
 }
 
+bool Renderer11::getPBOSupport() const
+{
+    return true;
+}
+
 float Renderer11::getTextureMaxAnisotropy() const
 {
     switch (mFeatureLevel)