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

device/generic_sensor/BUILD.gn

Index: device/generic_sensor/BUILD.gn
diff --git a/device/generic_sensor/BUILD.gn b/device/generic_sensor/BUILD.gn
index 280d58cd28d99eb1c5d9e4379b8935502cf14e32..debe2c933f1f2ae6a5bd4de9d0d7fd86223cb44f 100644
--- a/device/generic_sensor/BUILD.gn
+++ b/device/generic_sensor/BUILD.gn
@@ -17,11 +17,12 @@ component("generic_sensor") {
     "platform_sensor_ambient_light_mac.h",
     "platform_sensor_android.cc",
     "platform_sensor_android.h",
+    "platform_sensor_provider.cc",
     "platform_sensor_provider.h",
     "platform_sensor_provider_android.cc",
+    "platform_sensor_provider_android.h",
     "platform_sensor_provider_base.cc",
     "platform_sensor_provider_base.h",
-    "platform_sensor_provider_default.cc",
     "platform_sensor_provider_mac.cc",
     "platform_sensor_provider_mac.h",
     "sensor_impl.cc",
@@ -46,14 +47,11 @@ component("generic_sensor") {
       "android/sensors_jni_registrar.cc",
       "android/sensors_jni_registrar.h",
     ]
-    sources -= [ "platform_sensor_provider_default.cc" ]
 
     deps += [ ":jni_headers" ]
   }
 
   if (is_mac) {
-    sources -= [ "platform_sensor_provider_default.cc" ]
-
     deps += [ "//device/sensors/public/cpp" ]
 
     libs = [ "IOKit.framework" ]