Add build flag to enable DISCOVERY registration

Bug: 1043148
Change-Id: I0789a40948bf74123ce50685726034d11ceedbd5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2007764Reviewed-by: Peter Beverloo <peter@chromium.org>
Commit-Queue: Alex Chau <alexchau@chromium.org>
Cr-Commit-Position: refs/heads/master@{#733379}

chrome/browser/BUILD.gn

@@ -1962,6 +1962,7 @@ jumbo_static_library("browser") {
     "//chrome/browser/resource_coordinator:mojo_bindings",
     "//chrome/browser/resource_coordinator:tab_manager_features",
     "//chrome/browser/safe_browsing",
+    "//chrome/browser/sharing:buildflags",
     "//chrome/browser/sharing/proto",
     "//chrome/browser/ssl:proto",
     "//chrome/browser/touch_to_fill",

chrome/browser/sharing/BUILD.gn

+# 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.
+
+import("//build/buildflag_header.gni")
+import("//chrome/browser/sharing/buildflags.gni")
+
+buildflag_header("buildflags") {
+  header = "buildflags.h"
+  flags = [ "ENABLE_DISCOVERY=$enable_discovery" ]
+}

chrome/browser/sharing/buildflags.gni

+# 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.
+
+declare_args() {
+  enable_discovery = false
+}

chrome/browser/sharing/sharing_device_registration.cc

@@ -11,6 +11,7 @@
 #include "base/bind.h"
 #include "base/feature_list.h"
 #include "build/build_config.h"
+#include "chrome/browser/sharing/buildflags.h"
 #include "chrome/browser/sharing/click_to_call/feature.h"
 #include "chrome/browser/sharing/shared_clipboard/feature_flags.h"
 #include "chrome/browser/sharing/sharing_constants.h"
@@ -252,6 +253,9 @@ SharingDeviceRegistration::GetEnabledFeatures() const {
     enabled_features.insert(SharingSpecificFields::REMOTE_COPY);
   if (IsPeerConnectionSupported())
     enabled_features.insert(SharingSpecificFields::PEER_CONNECTION);
+#if BUILDFLAG(ENABLE_DISCOVERY)
+  enabled_features.insert(SharingSpecificFields::DISCOVERY);
+#endif
 
   return enabled_features;
 }