[ppapi] Merged two identical interface_name

In jumbo build experiments, two cc files both defined
interface_name<PPB_InputEvent_1_0>() which clashed since in
jumbo builds many cc files are compiled in the same translation unit.

This moves the shared code to a shared file.

Bug: 898475
Change-Id: I9ce58e837d663cb5c15ba2596c22812a41def4c0
Reviewed-on: https://chromium-review.googlesource.com/c/1297148
Reviewed-by: Bill Budge <bbudge@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Reviewed-by: Sam Clegg <sbc@chromium.org>
Commit-Queue: Daniel Bratell <bratell@opera.com>
Cr-Commit-Position: refs/heads/master@{#607601}
6 files changed