Bug 1362212 - Remove canPlayTelemetry from _delayedStartup. r=dao

Calling HTMLMediaElement.canPlayType() on the main thread will cause
us to do disk I/O to load system decoding libraries, so we shouldn't
do it on the main thread, let alone on the parent process' main thread.

I moved the telemetry into an idle service observer off main thread
into Gecko in the previous patch.


MozReview-Commit-ID: CH6LNNLzreJ

--HG--
extra : rebase_source : 9219c63b4f8e18d127988d1debcc8712037e5406

browser/base/content/browser.js

@@ -1547,20 +1547,6 @@ var gBrowserInit = {
       this.gmpInstallManager.simpleCheckAndInstall().then(null, () => {});
     }, {timeout: 1000 * 60});
 
-    // Report via telemetry whether we're able to play MP4/H.264/AAC video.
-    // We suspect that some Windows users have a broken or have not installed
-    // Windows Media Foundation, and we'd like to know how many. We'd also like
-    // to know how good our coverage is on other platforms.
-    // Note: we delay by 90 seconds reporting this, as calling canPlayType()
-    // on Windows will cause DLLs to load, i.e. cause disk I/O.
-    setTimeout(() => {
-      let v = document.createElementNS("http://www.w3.org/1999/xhtml", "video");
-      let aacWorks = v.canPlayType("audio/mp4") != "";
-      Services.telemetry.getHistogramById("VIDEO_CAN_CREATE_AAC_DECODER").add(aacWorks);
-      let h264Works = v.canPlayType("video/mp4") != "";
-      Services.telemetry.getHistogramById("VIDEO_CAN_CREATE_H264_DECODER").add(h264Works);
-    }, 90 * 1000);
-
     SessionStore.promiseInitialized.then(() => {
       // Bail out if the window has been closed in the meantime.
       if (window.closed) {