image_decoder service -> data_decoder service

Establishes a more generic service definition for a thing to do
sandboxed data decoding. This is just a rename of the existing
image_decoder service.

Since there is nothing Chrome specific about this service, and there is
now some motivation to use sandboxed image decoding outside of Chrome,
this also moves the packaging of the service from chrome into content.

BUG=697557
TBR=tsepez@chromium.org

Review-Url: https://codereview.chromium.org/2774463002
Cr-Commit-Position: refs/heads/master@{#459631}
37 files changed