Move kRestrictGoogleWebVisibility into variations_features.h.

Doing this allows us to avoid the below DCHECK encountered when running
the status quo tests. Having variations_features.h allows us to avoid
splitting the variations static_library into two because
variations_features can have its own target in the BUILD file.

...FATAL:feature_list.cc(472)]
Check failed: CheckFeatureIdentity(feature). RestrictGoogleWebVisibility

Bug: 1094303
Change-Id: I9ee3f02d8f3cde7398e759fe54b19cdc9ebb2271
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2410554
Commit-Queue: Caitlin Fischer <caitlinfischer@google.com>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#808032}

components/variations/BUILD.gn

@@ -17,6 +17,19 @@ buildflag_header("buildflags") {
   flags = [ "LARGE_VARIATION_KEY_SIZE=$large_variation_key_size_enabled" ]
 }
 
+component("variations_features") {
+  output_name = "variations_features"
+
+  defines = [ "IS_VARIATIONS_FEATURES_IMPL" ]
+
+  sources = [
+    "variations_features.cc",
+    "variations_features.h",
+  ]
+
+  deps = [ "//base" ]
+}
+
 static_library("variations") {
   sources = [
     "active_field_trials.cc",
@@ -86,6 +99,8 @@ static_library("variations") {
     ]
   }
 
+  public_deps = [ ":variations_features" ]
+
   deps = [
     ":buildflags",
     "proto",

components/variations/variations_associated_data.cc

@@ -17,13 +17,6 @@
 
 namespace variations {
 
-namespace internal {
-
-const base::Feature kRestrictGoogleWebVisibility{
-    "RestrictGoogleWebVisibility", base::FEATURE_DISABLED_BY_DEFAULT};
-
-}  // namespace internal
-
 namespace {
 
 // The internal singleton accessor for the map, used to keep it thread-safe.

components/variations/variations_associated_data.h

@@ -45,14 +45,6 @@
 
 namespace variations {
 
-namespace internal {
-// A feature that supports more finely-grained control over the transmission of
-// VariationIDs to Google web properties by allowing some VariationIDs to not be
-// transmitted in all contexts. See IsFirstPartyContext() in
-// variations_http_headers.cc for more details.
-extern const base::Feature kRestrictGoogleWebVisibility;
-}  // namespace internal
-
 typedef int VariationID;
 
 const VariationID EMPTY_ID = 0;

components/variations/variations_features.cc

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/variations/variations_features.h"
+
+namespace variations {
+
+namespace internal {
+
+const base::Feature kRestrictGoogleWebVisibility{
+    "RestrictGoogleWebVisibility", base::FEATURE_DISABLED_BY_DEFAULT};
+
+}  // namespace internal
+}  // namespace variations

components/variations/variations_features.h

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_VARIATIONS_VARIATIONS_FEATURES_H_
+#define COMPONENTS_VARIATIONS_VARIATIONS_FEATURES_H_
+
+#include "base/component_export.h"
+#include "base/metrics/field_trial.h"
+
+namespace variations {
+namespace internal {
+
+// A feature that supports more finely-grained control over the transmission of
+// VariationIDs to Google web properties by allowing some VariationIDs to not be
+// transmitted in all contexts. See IsFirstPartyContext() in
+// variations_http_headers.cc for more details.
+COMPONENT_EXPORT(VARIATIONS_FEATURES)
+extern const base::Feature kRestrictGoogleWebVisibility;
+
+}  // namespace internal
+}  // namespace variations
+
+#endif  // COMPONENTS_VARIATIONS_VARIATIONS_ASSOCIATED_DATA_H_
\ No newline at end of file

components/variations/variations_ids_provider.cc

@@ -14,6 +14,7 @@
 #include "base/strings/string_util.h"
 #include "components/variations/proto/client_variations.pb.h"
 #include "components/variations/variations_client.h"
+#include "components/variations/variations_features.h"
 
 namespace variations {