Finish removing GrContext param from onRefEncodedData

TBR=reed@roogle.com

Bug: skia:5485
Change-Id: Ia4ed45ffc39f2ba9a80d4a1001208079142ae985
Reviewed-on: https://skia-review.googlesource.com/14323
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: Matt Sarett <msarett@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
8 files changed