Bug 1287987 - Histogram for VIDEO_HIDDEN_PLAY_TIME_PERCENTAGE - r=francois,kamidphish

Telemetry probe, for feedback (using r? in mozreview) by telemetry peer.

Keying by audio presence and height range will help us better understand how
much benefit we should effectively get for the video population out there.

MozReview-Commit-ID: 2BlnlwW7b8W

--HG--
extra : rebase_source : 2e5dcc2ea56a579d9015b2a8012884f95de420f9

toolkit/components/telemetry/Histograms.json

@@ -8205,6 +8205,16 @@
     "n_buckets": 100,
     "bug_numbers": [1285419]
   },
+  "VIDEO_HIDDEN_PLAY_TIME_PERCENTAGE" : {
+    "alert_emails": ["ajones@mozilla.com", "gsquelart@mozilla.com"],
+    "expires_in_version": "55",
+    "description": "Percentage of total time spent playing video while element is hidden. Keyed by audio presence and by height ranges (boundaries: 240. 480, 576, 720, 1080, 2160), e.g.: 'V,0<h<=240', 'AV,h>2180'; and 'All' will accumulate all percentages. This is reported whenever an HTML Media Element is suspended or resumed, such as when the page is unloaded.",
+    "keyed": true,
+    "kind": "linear",
+    "high": 100,
+    "n_buckets": 50,
+    "bug_numbers": [1287987]
+  },
   "VIDEO_UNLOAD_STATE": {
     "alert_emails": ["ajones@mozilla.com"],
     "expires_in_version": "55",