Pass system layers through chain.

Previously if any layers were activated via properties the layers did not see
those as arguments. After this the layers have a complete list of what layers
are enabled. This is then used in the layers to guarantee ordering.

Bug: 27126420

Change-Id: I3a6a923e2564abc3f7c43b110d892539e4d4bfdb
diff --git a/vulkan/libvulkan/loader.h b/vulkan/libvulkan/loader.h
index 77c8ebe..cec0ff6 100644
--- a/vulkan/libvulkan/loader.h
+++ b/vulkan/libvulkan/loader.h
@@ -153,7 +153,7 @@
     LayerRef(const LayerRef&) = delete;
     LayerRef& operator=(const LayerRef&) = delete;
 
-    const char* GetName();
+    const char* GetName() const;
     uint32_t GetSpecVersion();
 
     // provides bool-like behavior