This change contains several new targets required to successfully build the public cast_shell for x86. This code also contributes to other public build variants, but these have not been tested.

Keeping these changes current to TOT will keep the BUILD.gn files current as the code base changes. There are several known issues noted in the TODOs, some of which are listed below.

* //chromecast:chromecast_locales_pak needs to be built.

* //chromecast/app:cast_shell_unittests is not building.

* logic pieces for internal builds are not tested.

BUG=516899 (internal b/17615224)

Review URL: https://codereview.chromium.org/1213333003

Cr-Commit-Position: refs/heads/master@{#341928}
11 files changed