I am using Eclipse Neon 3 (4.6.3), and all my projects have the Java 1.8 Project Facet:
I have a new project. On this new one, I cloned a GitHub Repository and then did an Import to create a Web Project from the cloned Git code.
On this new imported project, the Java 1.8 facet is missing.
I added JDK 1.8 to my Build Path as the JRE library: