Decouple PowerUsageMonitor{Impl} from //content/browser

content/test/BUILD.gn

Index: content/test/BUILD.gn
diff --git a/content/test/BUILD.gn b/content/test/BUILD.gn
index 50cef162868aaa032393fe756a05fef13ad288b3..19a3878cf5a3640c8116ddc337487556899e635b 100644
--- a/content/test/BUILD.gn
+++ b/content/test/BUILD.gn
@@ -1114,7 +1114,6 @@ test("content_unittests") {
     "../browser/notifications/platform_notification_context_unittest.cc",
     "../browser/notifications/type_converters_unittest.cc",
     "../browser/power_monitor_message_broadcaster_unittest.cc",
-    "../browser/power_usage_monitor_impl_unittest.cc",
     "../browser/presentation/presentation_service_impl_unittest.cc",
     "../browser/presentation/presentation_type_converters_unittest.cc",
     "../browser/quota/mock_quota_manager.cc",
@@ -1588,7 +1587,6 @@ test("content_unittests") {
     ]
     sources -= [
       "../browser/media/session/audio_focus_manager_unittest.cc",
-      "../browser/power_usage_monitor_impl_unittest.cc",
       "../browser/webui/url_data_manager_backend_unittest.cc",
     ]
     deps -= [ "//device/battery" ]