Rename buildflag_headers for consistency

This renames most of components. There are still a couple left, but
this patch started getting big.

Targets go from foo_features to foo_buildflags
And similarly the header now has buildflags in the name.

BUG=814485
TEST=covered by build
[email protected]

Change-Id: I321403895df9ddc988491c70a78507ec51434783
Reviewed-on: https://chromium-review.googlesource.com/943600
Commit-Queue: Scott Violet <[email protected]>
Reviewed-by: Nico Weber <[email protected]>
Cr-Commit-Position: refs/heads/master@{#540227}
diff --git a/chrome/browser/prefs/browser_prefs.cc b/chrome/browser/prefs/browser_prefs.cc
index b90fd69f..fe137a8 100644
--- a/chrome/browser/prefs/browser_prefs.cc
+++ b/chrome/browser/prefs/browser_prefs.cc
@@ -73,7 +73,7 @@
 #include "components/certificate_transparency/ct_policy_manager.h"
 #include "components/content_settings/core/browser/host_content_settings_map.h"
 #include "components/dom_distiller/core/distilled_page_prefs.h"
-#include "components/feature_engagement/features.h"
+#include "components/feature_engagement/buildflags.h"
 #include "components/flags_ui/pref_service_flags_storage.h"
 #include "components/gcm_driver/gcm_channel_status_syncer.h"
 #include "components/network_time/network_time_tracker.h"
@@ -84,7 +84,7 @@
 #include "components/ntp_snippets/sessions/foreign_sessions_suggestions_provider.h"
 #include "components/ntp_snippets/user_classifier.h"
 #include "components/ntp_tiles/most_visited_sites.h"
-#include "components/offline_pages/features/features.h"
+#include "components/offline_pages/buildflags/buildflags.h"
 #include "components/omnibox/browser/zero_suggest_provider.h"
 #include "components/password_manager/core/browser/password_bubble_experiment.h"
 #include "components/password_manager/core/browser/password_manager.h"