Use fake Input Device Settings with chrome://device-emulator

chrome/browser/BUILD.gn

Index: chrome/browser/BUILD.gn
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index 530b97246ad1e1434e9174532946716f98406ac6..1a43e108c9e7a291df0efec7d8c85d8989fb95a8 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -1220,11 +1220,15 @@ source_set("test_support") {
       "chromeos/policy/stub_enterprise_install_attributes.h",
       "chromeos/settings/device_settings_test_helper.cc",
       "chromeos/settings/device_settings_test_helper.h",
-      "chromeos/system/fake_input_device_settings.cc",
-      "chromeos/system/fake_input_device_settings.h",
     ]
     configs += [ "//build/config/linux/dbus" ]
     deps += [ "//chromeos:test_support" ]
+    if (is_official_build || !is_debug) {
+      sources += [
+        "chromeos/system/fake_input_device_settings.cc",
+        "chromeos/system/fake_input_device_settings.h",
+      ]
+    }
   }
 
   if (enable_configuration_policy) {