[Sensors] Allow Sensor API only on secure top-level browsing contexts and add frequency checks

third_party/WebKit/LayoutTests/sensor/ambient-light-sensor.html

Index: third_party/WebKit/LayoutTests/sensor/ambient-light-sensor.html
diff --git a/third_party/WebKit/LayoutTests/sensor/ambient-light-sensor.html b/third_party/WebKit/LayoutTests/sensor/ambient-light-sensor.html
index 340cd572d7dd92bbefffaa5ebe5205e6dec141bf..ebec93d04af02f1c9282713db70c9cc376493f36 100644
--- a/third_party/WebKit/LayoutTests/sensor/ambient-light-sensor.html
+++ b/third_party/WebKit/LayoutTests/sensor/ambient-light-sensor.html
@@ -17,6 +17,11 @@ function update_sensor_reading(buffer) {
   buffer[1] = kDefaultReadingValue;
 }
 
+test(() => assert_throws(
+    new RangeError(),
+    () => new AmbientLightSensor({frequency: -60})),

[timvolodine, 2016/09/19 16:52:13]

nit: also test for capping at 60?

[Mikhail, 2016/09/20 13:29:36]

Done.

+    'Test that negative frequency causes exception from constructor.');
+
 sensor_test(sensor => {
   let ambientLightSensor = new AmbientLightSensor({frequency: 60});

[timvolodine, 2016/09/19 16:52:13]

just curious here: does the frequency here mean 'max frequency'. ambient light
normally does not have a constant 'frequency' right?

[Mikhail, 2016/09/20 13:29:36]

that is more 'desired polling frequency', frequency can be passed to AML sensor
constructor via SensorOptions:
https://w3c.github.io/ambient-light/#ambient-light-sensor-interface

[timvolodine, 2016/09/20 17:46:37]

it's not exactly clear what 'desired polling frequency' even means in the
context of ambient light sensor, but that's probably a concern towards the spec
editors.

I was actually wondering if we are actively polling the shared memory buffer in
case of ambient light sensor (even if it remains constant)?

[Mikhail, 2016/09/21 10:00:42]

That is indeed being discussed in WG atm, however it might be easier to treat it
as something that is finally passed to
https://developer.android.com/reference/android/hardware/SensorManager.html#r...
as sampling polling period.
in this case the polling strategy will not poll the shared buffer until
'onreadingupdate' event is received from the platform.

   ambientLightSensor.start();