GitLab

Both the infobar and the infobar container were making use of various infobar
constants that were declared in components/ but (usually) defined in chrome/.
This was a symptom of having put code in the component that really probably
belonged in the embedder.

This CL hoists the relevant logic to a new cross-platform
InfoBarContainerDelegate class defined on the chrome side, which implements some
of the methods of InfoBarContainer::Delegate.  Platforms then subclass this to
implement the remaining, platform-specific bits.

This means that the constants in question now live solely in chrome/, avoiding a
bunch of link-time nastiness when trying to build the components code
separately.

BUG=382924
TEST=none
TBR=finnur

Review URL: https://codereview.chromium.org/793783003

Cr-Commit-Position: refs/heads/master@{#308046}