Create stubs for the FramebufferImpl class.

BUG=angle:841

Change-Id: I089409981604abe9c65c3019765d8d9eeffe38f5
Reviewed-on: https://chromium-review.googlesource.com/232381
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libANGLE/renderer/FramebufferImpl.h b/src/libANGLE/renderer/FramebufferImpl.h
index 1547a32..ae7be4b 100644
--- a/src/libANGLE/renderer/FramebufferImpl.h
+++ b/src/libANGLE/renderer/FramebufferImpl.h
@@ -26,6 +26,12 @@
     virtual GLsizei getSamples() const = 0;
 };
 
+class FramebufferImpl
+{
+  public:
+    virtual ~FramebufferImpl() {};
+};
+
 }
 
 #endif // LIBANGLE_RENDERER_FRAMBUFFERIMPL_H_