Reland "[pdf] SkPDFGraphicStackState::Entry::fColor default"

This reverts commit d2cfcc3b5189237f59f4b1fa7ace4ab353444121.

Reason for revert: Adding build flag

Original change's description:
> Revert "[pdf] SkPDFGraphicStackState::Entry::fColor default"
>
> This reverts commit fc31f43cc40abc90d09cb11c220a54cd70211b70.
>
> Reason for revert: Changes some users expectations. Will re-land with a build flag.
>
> Original change's description:
> > [pdf] SkPDFGraphicStackState::Entry::fColor default
> >
> > Make the default value for SkPDFGraphicStackState::Entry::fColor a very
> > invalid color instead of opaque black in order to better match the
> > actual defaults in PDF.
> >
> > Currently if an SkPDFDevice is created and the first thing done with it
> > is to draw an opaque black path then the opaque black will not be
> > written to the PDF since it is currently assumed that the default will
> > be opaque black. However, because no color space is currently defined
> > for the fill and stroke colors and PDF otherwise has no default, the
> > path will instead be filled with an indeterminate opaque color (in the
> > case of poppler this will be cyan).
> >
> > Change-Id: I9f6a46c42fe8721d6a6f3dddc5ac986207a64bcd
> > Reviewed-on: https://skia-review.googlesource.com/c/skia/+/635602
> > Reviewed-by: Herb Derby <herb@google.com>
> > Commit-Queue: Ben Wagner <bungeman@google.com>
>
> Change-Id: Ifc53ec0643549aad73cf15ac79bfe05c81d446a1
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/636076
> Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>

Change-Id: I8bd567b89d411142446b04419ff4cd58263b77b2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/636077
Commit-Queue: Ben Wagner <bungeman@google.com>
Reviewed-by: Herb Derby <herb@google.com>
2 files changed