[Nearby] Move prefs and enums to common directory

The //chrome/browser/nearby_sharing/ directory has subdirectories with
their own BUILD files. Those directories cannot currently depend on the
Nearby Share enum and pref files, which currently live in the
//chrome/browser/nearby_sharing/ directory. Here, we create a
//chrome/browser/nearby_sharing/common BUILD target that contains Nearby
Share prefs and enums.

Change-Id: I9e8daf5660ec4dc22ef002c3cc00a1d715bb5ad5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2306372
Commit-Queue: Josh Nohle <[email protected]>
Reviewed-by: James Vecore <[email protected]>
Reviewed-by: Alex Chau <[email protected]>
Reviewed-by: Lei Zhang <[email protected]>
Cr-Commit-Position: refs/heads/master@{#790539}
diff --git a/chrome/browser/prefs/browser_prefs.cc b/chrome/browser/prefs/browser_prefs.cc
index 4480b63a..b1bf7dd 100644
--- a/chrome/browser/prefs/browser_prefs.cc
+++ b/chrome/browser/prefs/browser_prefs.cc
@@ -237,7 +237,7 @@
 #include "chrome/browser/gcm/gcm_product_util.h"
 #include "chrome/browser/media/unified_autoplay_config.h"
 #include "chrome/browser/metrics/tab_stats_tracker.h"
-#include "chrome/browser/nearby_sharing/nearby_sharing_prefs.h"
+#include "chrome/browser/nearby_sharing/common/nearby_share_prefs.h"
 #include "chrome/browser/search/instant_service.h"
 #include "chrome/browser/search/promos/promo_service.h"
 #include "chrome/browser/search/search_suggest/search_suggest_service.h"