mono/MonoGame — pull request #2606 by danzel (2014-05-23 10:06:09+00:00)
Title: Fix burst of Game.Update calls at the start of the game

Found while investigating #2595
Test project: https://github.com/danzel/DrawTextTest/tree/isrunningslowlytest

We start the Game._gameTimer Stopwatch when the Game class is constructed. This is before we have done any of the system initialisation, which can take a while.
As such, the first time we get in to Tick, we think the game has already been running for quite a while and we need to do lots of Update calls to catch up (usually _maxElapsedTime worth).

Instead now we only start the StopWatch when we are about to start the Update/Draw loop.

With the above test project on XNA start up looks like (see out.txt):
```
Update 0 False,
Update 1 False,
Draw 0 False,
Update 2 False,
Update 3 False,
Draw 1 False,
Update 4 False,
Draw 2 False,
Update 5 False,
(And so on, Update Draw...)
```

But in Monogame it looked like:
```
Update 0 True,
Update 1 True,
Update 2 True,
Update 3 True,
Update 4 True,
Update 5 True,
Update 6 True,
Update 7 True,
Update 8 True,
Update 9 True,
Update 10 True,
Update 11 True,
Update 12 True,
Update 13 True,
Update 14 True,
Draw 0 True,
Update 15 True,
Update 16 True,
Update 17 True,
Draw 1 True,
Update 18 False,
Draw 2 False,
Update 19 False,
Draw 3 False,
(And so on)
```

Now the start of monogame looks like:
```
Update 0 False,
Draw 0 False,
Update 1 False,
Update 2 False,
Draw 1 False,
Update 3 False,
Draw 2 False,
Update 4 False,
Draw 3 False,
(silky smooth!)
```