The built in FPS overlay has a few problems that this one does not have, most of all: it is distracting.
1. The built in one also shows memory, which constantly fluctuates and garbage collects.
It is useful for devs profiling memory.
2. The built in one shifts around constantly because it is not monospace.
This locks "FPS:" into one position (the far top right corner of the canvas),
along with a locked position for the FPS value.