Revert "Query attachment render targets from Impl class." D3D9 bug is causing failures in the WebGL depth texture test. BUG=angleproject:963 This reverts commit 804e8436f91733e1d0f769ec10082e4741f2e549. Change-Id: I660f05033360e97258794138cb50b604f5ac16b6 Reviewed-on: https://chromium-review.googlesource.com/269005 Reviewed-by: Jamie Madill <jmadill@chromium.org> Tested-by: Jamie Madill <jmadill@chromium.org>