How to reproduce:
1. Open the user-submitted project ("shadergraph.zip")
2. Open the "Shaders" folder and reimport the "Back Face Color" subgraph
3. Observe the long reimport time/editor hanging
4. If the reimport doesn't hang repeat the 2nd step again (Occurs around 1/2 of the time)

Expected result: reimporting subgraphs doesn't take a really long time and the editor doesn't hang while doing so
Actual result: reimporting subgraphs takes a long time and occasionally hangs the editor

Reproduced in: 2019.2.0a7, 2019.1.0b6 (With ShaderGraph 5.6.1; 5.3.1; 5.2.3)

Note: This error is thrown occasionally when reimporting subgraphs

"ShaderSubGraphImporterEditor.OnInspectorGUI must call ApplyRevertGUI to avoid unexpected behaviour.
UnityEditor.Experimental.AssetImporters.AssetImporterEditor:OnDisable()"