Launching onto HTML5 will fail during the compiling stage.  The following error will occur when the project is launched in the browser and begins compiling: 
Uncaught TypeError: Browser.mainLoop.scheduler is not a function
Result: Project will fail to run due to a TypeError.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-36937 in the post.
| 1 | 
| Component | UE - Platform - Mobile | 
|---|---|
| Affects Versions | 4.14, 4.15 | 
| Target Fix | 4.14 | 
| Fix Commit | 3181849 | 
|---|
| Created | Oct 6, 2016 | 
|---|---|
| Resolved | Nov 1, 2016 | 
| Updated | Apr 27, 2018 |