Here's a summary of the profile 22.4% in display list building 13.9% in BuildContainerLayerFor 4.4% in WillEndTransaction 37.7% in DrawPaintedLayer - 22% in CanvasBackgroundColor - 17.4% in Text - 13% in DisplayImage - 11% in BackgroundColor 13.6% in ValidateTile Nothing suggests that we are painting particularly slowly. i.e having 22% of painting in CanvasBackgroundColor (basically memset) suggests that we are painting pretty fast. I expect the big problems here are the non-paint overhead and the fact that we might be painting too much and not the right stuff.
Side note, this is on OS X. 22% spent in CanvasBackgroundColor still seems too slow. I see chunks of 8ms to paint a background color. That seems really bad. There is even one chunk that is 17 ms, which is a whole frame.