FramebufferD3D: Only make sure that enabled attachments are not the same.

It's acceptable to have the same object attached to muliple framebuffer
attachments if they are not being drawn to.

This was triggering failures in the conformance2/state/gl-object-get-calls.html
test.

BUG=483282

Change-Id: If088ccd9b1189f060dfa33ebbe4d82f1f47559b0
Reviewed-on: https://chromium-review.googlesource.com/354570
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libANGLE/Framebuffer.h b/src/libANGLE/Framebuffer.h
index 0fd0423..f558793 100644
--- a/src/libANGLE/Framebuffer.h
+++ b/src/libANGLE/Framebuffer.h
@@ -58,6 +58,7 @@
 
     const std::string &getLabel();
 
+    const FramebufferAttachment *getAttachment(GLenum attachment) const;
     const FramebufferAttachment *getReadAttachment() const;
     const FramebufferAttachment *getFirstColorAttachment() const;
     const FramebufferAttachment *getDepthOrStencilAttachment() const;
@@ -75,6 +76,9 @@
 
     bool attachmentsHaveSameDimensions() const;
 
+    const FramebufferAttachment *getDrawBuffer(size_t drawBufferIdx) const;
+    size_t getDrawBufferCount() const;
+
   private:
     friend class Framebuffer;