Update CHANGELOG.md

Author: photonstorm

CHANGELOG.md

@@ -61,6 +61,7 @@
 * `RequestAnimationFrame.target` is a new property that controls the fps rate (in ms) when setTimeout is used (thanks @pavels)
 * The `WebAudioSoundManager.unlock` method will now listen for `keydown` events in order to unlock the Audio Context, as well as touch and pointer events, making it more accessible (thanks Nick Tipping)
 * The `requestAnimationFrame` polyfill no longer expects a Browserify environment and uses `window` through-out, it also no longer adds in the same as performance.now does.
+* `BitmapText.getTextBounds` didn't reset the dirty flag, causing the `GetBitmapTextSize` function to be called every time the Bitmap Text was rendered. With enough text objects on-screen this could negatively impact performance. The flag is now reset every time the bounds are recalculated.
 
 ### Bug Fixes