Thanks for the info. Quick summary of my situation:
1) One canvas object, about 50% of the screen, used exclusively to draw lines (drawing with your finger).
2) With CJS 1.3, performance on iOS was great (60 fps). Performance was stellar in Chrome as well.
3) After CJS 1.4, performance on iOS dropped to 9 FPS even when idle. Performance in Chrome is still excellent.
4) I tried disabling WebGL for my app, but it won't launch on iOS at all due to the memory management that is lost (several layouts with large images that work totally fine when they are only loaded into RAM when that layout is active - which is what CJS 1.4 introduced, apparently leveraging WebGL to do it).
Now that I understand more what's happening, it makes sense to me why all three statements above happened. So, at this point, I'm trying to figure out how to creatively work around the inherent performance hit of using WebGL and canvas together.
Think it would be possible to only spawn a very small canvas object when the user touches the screen that follows the finger and somehow "paste" the trailing line to the screen?
As a final note, I'm certain the glw error is not related to performance. I've been unable to figure out how to work around it, although I got lucky a few times and was able to exit out of the layout without getting the error, but I can't reliably reproduce that.