Is the only purpose of this to support color management? Won't color management
already work by attaching the right color spaces to the display list itself?

No, it does not work that way. Skia only has colorspace tagging for input and outputs, SkPictures are neither.  Doing this will also fix other problems, not just color management. Among other things, we will be able to start using deferred image decoding for images drawn into a canvas.

Update: we should use preferred raster *bounds* rather than scale, to avoid
loss of precision when multiplying up by a scale to the preferred scale, and
also to account for scales that do not preserve aspect ratio.

Sorry, updated the wrong bug there. But in any case, it should be bounds not
scale.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a1caccf274a8013424414b3b306c3c7a4f7d4d42

commit a1caccf274a8013424414b3b306c3c7a4f7d4d42
Author: chrishtr <chrishtr@chromium.org>
Date: Fri Oct 21 03:48:28 2016

Plumb preferred raster bounds rather than scale

This allows us to specify exactly the preferred raster size of the
intrinsic object, such a images, without rounding error due to
floating-point, conflation of width/height due to not preserving
aspect ratio, etc.

BUG= 657431 
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_precise_blink_rel

Review-Url: https://chromiumcodereview.appspot.com/2441853002
Cr-Commit-Position: refs/heads/master@{#426719}

[modify] https://crrev.com/a1caccf274a8013424414b3b306c3c7a4f7d4d42/cc/blink/web_layer_impl.cc
[modify] https://crrev.com/a1caccf274a8013424414b3b306c3c7a4f7d4d42/cc/blink/web_layer_impl.h
[modify] https://crrev.com/a1caccf274a8013424414b3b306c3c7a4f7d4d42/cc/layers/layer.cc
[modify] https://crrev.com/a1caccf274a8013424414b3b306c3c7a4f7d4d42/cc/layers/layer.h
[modify] https://crrev.com/a1caccf274a8013424414b3b306c3c7a4f7d4d42/cc/layers/layer_impl.cc
[modify] https://crrev.com/a1caccf274a8013424414b3b306c3c7a4f7d4d42/cc/layers/layer_impl.h
[rename] https://crrev.com/a1caccf274a8013424414b3b306c3c7a4f7d4d42/third_party/WebKit/LayoutTests/compositing/scaling/preferred-raster-bounds-expected.txt
[rename] https://crrev.com/a1caccf274a8013424414b3b306c3c7a4f7d4d42/third_party/WebKit/LayoutTests/compositing/scaling/preferred-raster-bounds.html
[modify] https://crrev.com/a1caccf274a8013424414b3b306c3c7a4f7d4d42/third_party/WebKit/Source/core/paint/BoxPainter.cpp
[modify] https://crrev.com/a1caccf274a8013424414b3b306c3c7a4f7d4d42/third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in
[modify] https://crrev.com/a1caccf274a8013424414b3b306c3c7a4f7d4d42/third_party/WebKit/Source/platform/graphics/GraphicsLayer.cpp
[modify] https://crrev.com/a1caccf274a8013424414b3b306c3c7a4f7d4d42/third_party/WebKit/Source/platform/graphics/GraphicsLayer.h
[modify] https://crrev.com/a1caccf274a8013424414b3b306c3c7a4f7d4d42/third_party/WebKit/public/platform/WebLayer.h

Obsolete.