Memory leak with canvas context clearRect and fillText

[JohnKlenk]

There is a significant memory leak (equally in 1.3 and 1.4) with canvas context clearRect and fillText. fillText() is worse, at nearly 400 bytes each time it is called. fillRect() does not appear to leak.

We created a tiny html file (canvasleak.zip), which you can load in ultralight's "Sample 8 - Web Browser" that demonstrates the leak at a rate of over 1GB per minute so that it can be easily observed, as smaller leaks can be tricky to notice amid the normal ups and downs of allocation and garbage collection. Click on the page to begin the animation and again to pause it. It counts off seconds and frames so that you can easily measure out a minute of memory leak which occurs at a rate of approximately 500KB/frame. It uses 1000 canvases, feel free to change the settings--you can observe the same leak with a single canvas (just a lot slower).

[adamjs]

Thanks for the report, I've applied a mitigation for this in 1.4 trunk that significantly reduces the memory growth (should be live now in latest 1.4-dev bins). A full fix actually requires an allocator rehaul so that we can share resources more intelligently (now planned in 1.4.1).

[JohnKlenk]

Thanks. I'm seeing about a 50% improvement with the latest dev build.