GitLab

Previously the API build targets from //extensions/shell were used
to simplify the porting process. As we will be needing to extend this
with custom features this moves the shell API build files and changes
them to be correct for chromecast

This also adds content_scripts from chrome and custom cast_url
manifest features to match the removed code

Bug: b/73383411
Test: Load local extension verify things still work
Change-Id: I4e3a08e463ed7560c93ac45d7a4295dfdca8e4d4
Reviewed-on: https://chromium-review.googlesource.com/963074
Commit-Queue: Albert Chaulk <achaulk@chromium.org>
Reviewed-by: Luke Halliwell <halliwell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543820}