reland: Rename buildflag_headers for consistency

This renames targets in chrome, chromecast and chromeos.

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],[email protected]

Change-Id: I35f82bb244d2f8bd745d3157f266bae99f21f888
Reviewed-on: https://chromium-review.googlesource.com/935296
Reviewed-by: Scott Violet <[email protected]>
Commit-Queue: Scott Violet <[email protected]>
Cr-Commit-Position: refs/heads/master@{#538905}
diff --git a/chrome/browser/io_thread.h b/chrome/browser/io_thread.h
index 2c58c618..8e3ec06 100644
--- a/chrome/browser/io_thread.h
+++ b/chrome/browser/io_thread.h
@@ -23,7 +23,7 @@
 #include "build/build_config.h"
 #include "chrome/browser/net/chrome_network_delegate.h"
 #include "chrome/browser/net/system_network_context_manager.h"
-#include "chrome/common/features.h"
+#include "chrome/common/buildflags.h"
 #include "components/metrics/data_use_tracker.h"
 #include "components/prefs/pref_member.h"
 #include "components/ssl_config/ssl_config_service_manager.h"