Implement CHROMIUM_copy_compressed_texture for D3D11.

BUG=angleproject:1356

Change-Id: Id563997d2921cf558c52a781ae66d8bde58d1f2f
Reviewed-on: https://chromium-review.googlesource.com/339847
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libANGLE/renderer/TextureImpl.cpp b/src/libANGLE/renderer/TextureImpl.cpp
index 465d4e3..af47963 100644
--- a/src/libANGLE/renderer/TextureImpl.cpp
+++ b/src/libANGLE/renderer/TextureImpl.cpp
@@ -40,4 +40,11 @@
     UNREACHABLE();
     return gl::Error(GL_INVALID_OPERATION, "CHROMIUM_copy_texture exposed but not implemented.");
 }
+
+gl::Error TextureImpl::copyCompressedTexture(const gl::Texture *source)
+{
+    UNREACHABLE();
+    return gl::Error(GL_INVALID_OPERATION,
+                     "CHROMIUM_copy_compressed_texture exposed but not implemented.");
+}
 }