It is desirable that, when layer hoisting is disabled, the MPD and non-MPD timings be
roughly the same. Unfortunately, using a separate canvas for each tile (a requirement
for MPD) introduces its own discrepancy into the timing. Using a separate canvas for
each tile doesn't seem to make a difference for 8888 (see the non-MPD 8888 column below)
but slows down GPU rendering (see the non-MPD GPU column below). Since this is how
Chromium renders I propose switching to this regimen (even though it is "slowing down"
GPU rendering).
nanobench mean times (ms) with layer hoisting disabled (for desk_amazon.skp)
8888
MPD non-MPD
1 canvas (old-style) 0.628 1.71
separate (new-style) 0.795 1.63
GPU
MPD non-MPD
1 canvas (old-style) 2.34 1.69
separate (new-style) 2.32 2.66
Review URL: https://codereview.chromium.org/779643002
Two issues with the SKPBench tile computation were causing the MPD path to do more work:
The clip from the parent canvas wasn't being used to trim content off the edges of the MPD tiles
The non-MPD path was not taking the scale into account in its tile placement (resulting in it having fewer, larger active tiles when scaling).
Review URL: https://codereview.chromium.org/776273002
