Add support for rebaselining from trybots.

This adds support to rebaseline_server to fetch actual results from
tryjobs run on rietveld issues.

Review URL: https://codereview.chromium.org/688353003
Rebaseline problem (Galaxy S4) multipicturedraw GMs

This CL rebaselines the buggy multipicturedraw GMs related to:

Always enable layer hoisting in Skia (https://codereview.chromium.org/698493002/)

TBR=jcgregorio@google.com

BUG=skia:3116

Review URL: https://codereview.chromium.org/715823002
Remove bogus assert

content key can be set after pending io scheduled (e.g. when scaling up a npot texture to pot).

BUG=skia:2889
TBR=robertphillips@google.com

Review URL: https://codereview.chromium.org/693843004
remove separate color from coverage

BUG=skia:

Review URL: https://codereview.chromium.org/699023003
more gms to ignore

TBR=
BUG=skia:

Review URL: https://codereview.chromium.org/691143006
Remove multipicturedraw GMs from ignored-tests.txt

TBR=jcgregorio@google.com

Review URL: https://codereview.chromium.org/718763002
Fix Android framework build.

Need to include (transitively) SkUserConfig before checking
SK_SUPPORT_GPU.

Review URL: https://codereview.chromium.org/693613005