Add support for the remaining ES3 framebuffer attachment parameter queries.

TRAC #23474

Author: Geoff Lang
Signed-off-by: Jamie Madill
Signed-off-by: Shannon Woods
diff --git a/src/libGLESv2/Framebuffer.cpp b/src/libGLESv2/Framebuffer.cpp
index 86c6269..92b18bd 100644
--- a/src/libGLESv2/Framebuffer.cpp
+++ b/src/libGLESv2/Framebuffer.cpp
@@ -269,6 +269,11 @@
     return mStencilbuffer.get();
 }
 
+Renderbuffer *Framebuffer::getDepthStencilBuffer() const
+{
+    return (mDepthbuffer.id() == mStencilbuffer.id()) ? mDepthbuffer.get() : NULL;
+}
+
 Renderbuffer *Framebuffer::getDepthOrStencilbuffer() const
 {
     Renderbuffer *depthstencilbuffer = mDepthbuffer.get();