MoveToContentAsync is often called in states where it will immediately
return true without any reading. In this case return AsyncUtils.True
avoiding allocation or async state-machine.
DoReadAsync is a very heavily hit method, and can often be fulfilled
without creating another state machine, so do this.
The remaining looping async case is the only use of ParsePostValueAsync,
so inline it into the calling method, so there is one less task
allocation.
Return value of EatWhitespaceAsync is never used, returning void reduces
the number of locals an hence the size of the state-machine. Do the same
for EatWhitespace though the impact is less.
Jon Hanna
dcae8e220d