Put more files under the enable_service_discovery build flag.

chrome/browser/devtools/BUILD.gn

Index: chrome/browser/devtools/BUILD.gn
diff --git a/chrome/browser/devtools/BUILD.gn b/chrome/browser/devtools/BUILD.gn
index 06b35f698938f875c1fafec4b510a81133807329..22ffc2336132baf6f00c4a1de6266ee4d3ff75bd 100644
--- a/chrome/browser/devtools/BUILD.gn
+++ b/chrome/browser/devtools/BUILD.gn
@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 if (!is_android) {
+  import("//build/config/features.gni")
   import("//tools/grit/grit_rule.gni")
 }
 
@@ -92,8 +93,6 @@ static_library("devtools") {
       "device/android_device_manager.cc",
       "device/android_device_manager.h",
       "device/android_web_socket.cc",
-      "device/cast_device_provider.cc",
-      "device/cast_device_provider.h",
       "device/devtools_android_bridge.cc",
       "device/devtools_android_bridge.h",
       "device/port_forwarding_controller.cc",
@@ -133,5 +132,11 @@ static_library("devtools") {
       "remote_debugging_server.cc",
       "remote_debugging_server.h",
     ]
+    if (enable_service_discovery) {
+      sources += [
+        "device/cast_device_provider.cc",
+        "device/cast_device_provider.h",
+      ]
+    }
   }
 }