[sensors] Add a browser test to sanity check ambient light sensor.

content/test/BUILD.gn

Index: content/test/BUILD.gn
diff --git a/content/test/BUILD.gn b/content/test/BUILD.gn
index 9c60ce1322b010ea7b58c9b294b3ef31fec1000d..07dc54afdef381bd0052a58938a3f4d0baad1782 100644
--- a/content/test/BUILD.gn
+++ b/content/test/BUILD.gn
@@ -561,6 +561,7 @@ test("content_browsertests") {
     "../browser/frame_host/render_frame_host_manager_browsertest.cc",
     "../browser/frame_host/render_frame_message_filter_browsertest.cc",
     "../browser/frame_host/render_widget_host_view_child_frame_browsertest.cc",
+    "../browser/generic_sensor_browsertest.cc",
     "../browser/gpu/gpu_ipc_browsertests.cc",
     "../browser/host_zoom_map_impl_browsertest.cc",
     "../browser/iframe_zoom_browsertest.cc",
@@ -673,6 +674,7 @@ test("content_browsertests") {
     "//device/base/synchronization",
     "//device/battery",
     "//device/battery:mojo_bindings",
+    "//device/generic_sensor",
     "//device/power_save_blocker",
     "//device/sensors/public/cpp",
     "//device/vibration:mojo_bindings",