Bug 1423241 - Remove drawImage exception handling from captureStream_common.js. r=jib

This can conceal real bugs. Tests should be fixed so they don't risk calling
getPixel in invalid states instead.

Differential Revision: https://phabricator.services.mozilla.com/D9100

--HG--
extra : moz-landing-system : lando

dom/canvas/test/captureStream_common.js

@@ -128,12 +128,8 @@ CaptureStreamTestHelper.prototype = {
       if (aborted) {
         throw await cancel;
       }
-      try {
-        if (test(this.getPixel(video, offsetX, offsetY, width, height))) {
-          return;
-        }
-      } catch (e) {
-        info("Waiting for pixel but no video available: " + e + "\n" + e.stack);
+      if (test(this.getPixel(video, offsetX, offsetY, width, height))) {
+        return;
       }
     }
   },

dom/media/tests/mochitest/test_getUserMedia_bug1223696.html

@@ -24,10 +24,13 @@
       video.play();
 
       var h = new CaptureStreamTestHelper2D();
-      var removedTrack = stream.getVideoTracks()[0];
-      stream.removeTrack(removedTrack);
+      var removedTrack;
       video.onloadeddata = () => {
         info("loadeddata");
+
+        removedTrack = stream.getVideoTracks()[0];
+        stream.removeTrack(removedTrack);
+
         var canvas = document.createElement("canvas");
         canvas.getContext("2d");
         var canvasStream = canvas.captureStream();