[wpe-webkit] ImageBuffer refactoring

[Said Abou-Hallawa]

Hello,

I did an extensive code refactoring for ImageBuffer to allow canvas GPU rendering. I had to refactor all ports so that we  make a single decision at the time of creating the ImageBuffer and then we do not have to do any other change in the canvas code.

The good thing about this code refactoring is it allows canvas GPU rendering for all ports. So GTK, WPE and WinCairo ports do not need do anything expect enabling it in the future. The bad thing is I was able to compile and link my changes on these ports only. I could not verify it does paint the canvas correctly. I also could not run the layout tests.

So I need your help reviewing the Cairo changes in the patch https://bugs.webkit.org/show_bug.cgi?id=204955 and running the layout tests especially LayoutTests/canvas and LayoutTests/fast/canvas. I really appreciate sharing your suggestions and the LayoutTests results.

Thanks,
Said