Fixed Chrome OS component GN build.

Component build was broken since 4a84927b, where
chromeos::device_event_log was moved  to components.

TBR=reillyg@chromium.org,derat@chromium.org
BUG=none

Review URL: https://codereview.chromium.org/971363002

Cr-Commit-Position: refs/heads/master@{#318875}

ui/chromeos/BUILD.gn

@@ -46,6 +46,7 @@ component("ui_chromeos") {
     "//base/third_party/dynamic_annotations",
     "//chromeos:chromeos",
     "//chromeos:power_manager_proto",
+    "//components/device_event_log",
     "//skia",
     "//ui/aura",
     "//ui/base",