Export CanonOutputT template instantiations to avoid double definition.

The double instantiations seem to happen because of virtual methods. If
the class could lose be non-virtual, this could be fixed. However, this
is blocking another CL and this fix is the optimal one with regards to
time constraints.

Bug: 747081
Change-Id: I5c2d2cc7a9e49266b25d2cd3d9835d0647e5438a
Reviewed-on: https://chromium-review.googlesource.com/579211
Commit-Queue: Mounir Lamouri <[email protected]>
Reviewed-by: Jochen Eisinger <[email protected]>
Reviewed-by: Daniel Cheng <[email protected]>
Cr-Commit-Position: refs/heads/master@{#508734}
7 files changed