Respect colorSpace in DecodingImageGenerator::onGetPixels()

ImageDecoder.cpp
In case the of a rare image with an embedded color space that
is not parametric, we will do a color space xform at decode
time.  Otherwise, leave it as is.

DecodingImageGenerator.cpp
Based on cc behavior, we should almost always be asking for
the SkImage "as is" (in the same color space that it is
already in).  In the rare case that we miss the cc cache and
request it in a different color space, will need to do the
color space xform here.

We always use an unpremul decoder when we will be doing a
color space xform in a second pass.  That way we don't
need to unpremultiply.

BUG=706613

Review-Url: https://codereview.chromium.org/2787053004
Cr-Commit-Position: refs/heads/master@{#464458}
9 files changed