The shader PkFxDepthCopy no longer compiles for GLES3, Metal and OpenGLCore (and vulkan, apparently) after switching from Unity 5.4 to Unity 5.5 and gives the error :
"Shader compiler: internal error compiling shader snippet type=[0|1] platform=<platform_id>: Protocol error - failed to read correct magic number"

To reproduce:
1. Open attached project
2. Select the shader in Resources/PkFxDepthCopy
3. In the inspector, drop down on the "Compile and show code", make sure one of the problematic APIs is selected
4. Click "compile and show code"

Expected Result: Shader should compile without errors

Reproducible: 5.5.0b3
Regression from 5.4.1f1