layers: Account for read-only depthstencil attachments in ValidateLayout

The depth stencil attachment can be DEPTH_STENCIL_READ_ONLY_OPTIMAL.

Signed-off-by: Chris Forbes <chrisforbes@google.com>
diff --git a/tests/layer_validation_tests.cpp b/tests/layer_validation_tests.cpp
index c8b4b90..2a61f42 100644
--- a/tests/layer_validation_tests.cpp
+++ b/tests/layer_validation_tests.cpp
@@ -12306,14 +12306,14 @@
     // perf warning for GENERAL layout on DS attachment
     m_errorMonitor->SetDesiredFailureMsg(
         VK_DEBUG_REPORT_PERFORMANCE_WARNING_BIT_EXT,
-        "Layout for depth attachment is GENERAL but should be DEPTH_STENCIL_ATTACHMENT_OPTIMAL.");
+        "GENERAL layout for depth attachment may not give optimal performance.");
     vkCreateRenderPass(m_device->device(), &rpci, NULL, &rp);
     m_errorMonitor->VerifyFound();
     // error w/ non-ds opt or GENERAL layout for color attachment
     attach.layout = VK_IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL;
     m_errorMonitor->SetDesiredFailureMsg(
         VK_DEBUG_REPORT_ERROR_BIT_EXT,
-        "Layout for depth attachment is VK_IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL but can only be DEPTH_STENCIL_ATTACHMENT_OPTIMAL or GENERAL.");
+        "Layout for depth attachment is VK_IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL but can only be DEPTH_STENCIL_ATTACHMENT_OPTIMAL, DEPTH_STENCIL_READ_ONLY_OPTIMAL or GENERAL.");
     vkCreateRenderPass(m_device->device(), &rpci, NULL, &rp);
     m_errorMonitor->VerifyFound();
     // For this error we need a valid renderpass so create default one