[jumbo] Merge two identical kFaviconsPerCategoryImage constants

In some jumbo build experiments (not official) there was an
identical constant in two explore_sites files. In jumbo builds
many cc files are merged into one translation unit for much
faster compilation.

This moves the constant to a header where it can be reused.

Change-Id: Id460645a39d69999bf2227c25651d1149f1a6d6c
Reviewed-on: https://chromium-review.googlesource.com/c/1275895
Commit-Queue: Justin DeWitt <dewittj@chromium.org>
Reviewed-by: Justin DeWitt <dewittj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600172}
3 files changed