use SkDocument to capture pdfs from SampleApp 'e'

BUG=skia:
TBR=
NOTRY=True

Review URL: https://codereview.chromium.org/634293004
Revert of Use presence of a content key as non-scratch indicator (patchset #5 id:80001 of https://codereview.chromium.org/639873002/)

Reason for revert:
breaking nanobench on ubuntu

Original issue's description:
> Use presence of a content key as non-scratch indicator
>
> BUG=skia:2889
>
> Committed: https://skia.googlesource.com/skia/+/9eefe0851eeaa8ded05b4774ebcb38ed201d5dbf

TBR=robertphillips@google.com
NOTREECHECKS=true
NOTRY=true
BUG=skia:2889

Review URL: https://codereview.chromium.org/642493003
Remove ~GrIORef since last remaining virtual and now all inline

TBR=reed@google.com
NOTRY=true

Review URL: https://codereview.chromium.org/638003003
call derived ~ from GrIORef

TBR=mtklein@google.com
NOTREECHECKS=true

Review URL: https://codereview.chromium.org/641813002