GitLab

Makes the IDL compiler processes runtime_enabled_features.json5
and makes Exposure aware of context-dependent and context-
independent runtime enabled features.

Bug: 839389
Change-Id: I2d46730f22866f6f677a96dbd7a72644253e4692
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1892973
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#711998}