Rename buildflag_headers for consistency

This finishes components.

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: I109f65c850229fc381ee70db2a6075f7fea05f31
Reviewed-on: https://chromium-review.googlesource.com/946519
Commit-Queue: Scott Violet <[email protected]>
Reviewed-by: John Abd-El-Malek <[email protected]>
Cr-Commit-Position: refs/heads/master@{#540696}
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 872086c..12e01ca 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -76,11 +76,11 @@
 #include "components/security_state/core/features.h"
 #include "components/security_state/core/security_state.h"
 #include "components/signin/core/browser/profile_management_switches.h"
-#include "components/signin/core/browser/signin_features.h"
+#include "components/signin/core/browser/signin_buildflags.h"
 #include "components/signin/core/browser/signin_switches.h"
 #include "components/spellcheck/common/spellcheck_features.h"
 #include "components/spellcheck/common/spellcheck_switches.h"
-#include "components/spellcheck/spellcheck_build_features.h"
+#include "components/spellcheck/spellcheck_buildflags.h"
 #include "components/ssl_config/ssl_config_switches.h"
 #include "components/suggestions/features.h"
 #include "components/sync/driver/sync_driver_switches.h"