The pattern of gen context, share context, free context, then allocate
a shared GL object in the second context would cause a use-after-free
of the ContextImpl as a GLFactory. Fix this by passing the factory
as a parameter to the resource manager allocation methods instead of
storing the factory pointer. This allows the same ResourceManager to
work with separate Context implementations, which will work with
non-virtual contexts.

BUG=612931

Change-Id: Ifceeb893bebd072f318963d935ff9d17181f5305
Reviewed-on: https://chromium-review.googlesource.com/347463Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/347468Reviewed-by: Jamie Madill <jmadill@chromium.org>