Download the Windows 10 SDK (this works on older versions of Windows as well): https://dev.windows.com/en-us/downloads/windows-10-sdk
Make sure Windows Performance Toolkit is checked (I usually just install everything).
Navigate to: C:\Program Files (x86)\Windows Kits\10\Windows Performance Toolkit\gpuview
Replace log.cmd with the contents from here:
(This just adds the TRACE_VR lines with the guid we use for tracking events in SteamVR).
(If you are using the Win8.1 ADK: http://pastebin.com/jEWDMbhz)
Open a command prompt at this location with Admin privileges.
Run 'log' to start capturing.
Wait maybe a second once it gets through loading things (the captured data size adds up fast!).
Then run 'log' again to stop capturing (followed by a rather lengthy merge process).
Run 'gpuview' and select merged.etl to view.