How to reproduce:
1. Create and open a new HDRP project
2. Create and open a new PBR graph
3. Add an exposure node and attach its output to the Master's Emission
4. Select the Exposure node and convert it into a subgraph
5. Observe the broken node and the error in the console window

Expected result: the node is still attached to the master with no issues
Actual result: the node breaks and throws a "undeclared identifier 'GetCurrentExposureMultiplier' at line 34 (on d3d11)" error

Reproduced in: 2019.3.0a7, 2019.2.0b8, 2019.1.8f1 (With HDRP/Shadergraph version: 6.7.1; 6.5.3; 5.16.1)
Couldn't test with: 2018.4.3f1 (No availiable package version with the exposure node)