[Icons NTP] Using flag to enable large icons on the NTP.
A follow-up to crrev.com/1026053003: We need to pass the flag for
enabling icon NTP to the 3 end points that use them. One endpoint
(searchbox_extetnsion.cc) is in the Renderer process, and the flag (as
command line) needs to be propagated. To obey existing dependencies,
the flags kDisableIconNtp and kEnableIconNtp need to be moved to
ui_base_witches.*. As for enabling using variation, the code is kept
near the end points to avoid adding dependency to ui_base.
BUG=467712
Review URL: https://codereview.chromium.org/1043753002
Cr-Commit-Position: refs/heads/master@{#323570}
8 files changed
