Engine DDC doesn't appear to be included with fresh install of 4.15 Engine.
Upon launching editor for first time, ShaderCompileWorker Process startup and user gets notification shaders are compiling.
Results: The editor stalls at 45% and then opens to project browser where user sees notification with progress of shaders compiling.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-39968 in the post.