Mark AmbientLightSensor.https.html as a slow test.

ALS and Magnetometer have a maximum frequency of 10Hz, which can cause the
Generic Sensors test suite to take longer than normal to run.

Add the <meta> tag with the annotation to AmbientLightSensor.https.html, as
Magnetometer.https.html already has it.

Bug: 731018
Change-Id: Ia437fb2907c0e52caa281c8e709c1d48ca59873f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2203071
Auto-Submit: Raphael Kubo da Costa <raphael.kubo.da.costa@intel.com>
Commit-Queue: Reilly Grant <reillyg@chromium.org>
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#769453}
diff --git a/ambient-light/AmbientLightSensor.https.html b/ambient-light/AmbientLightSensor.https.html
index 2383a2d..7d23896 100644
--- a/ambient-light/AmbientLightSensor.https.html
+++ b/ambient-light/AmbientLightSensor.https.html
@@ -1,6 +1,7 @@
 <!DOCTYPE html>
 <meta charset="utf-8">
 <title>AmbientLightSensor Test</title>
+<meta name="timeout" content="long">
 <link rel="author" title="Intel" href="http://www.intel.com">
 <link rel="help" href="https://www.w3.org/TR/ambient-light/">
 <script src="/resources/testharness.js"></script>