Bug 1228841 - Part 0: Remove remaining conditional catch consumers in dom/. r=billm

dom/media/tests/mochitest/test_peerConnection_transceivers.html

@@ -423,11 +423,12 @@
       pc.addTransceiver("foo");
       ok(false, 'addTransceiver("foo") throws');
     }
-    catch (e if e instanceof TypeError) {
-      ok(true, 'addTransceiver("foo") throws a TypeError');
-    }
     catch (e) {
-      ok(false, 'addTransceiver("foo") throws a TypeError');
+      if (e instanceof TypeError) {
+        ok(true, 'addTransceiver("foo") throws a TypeError');
+      } else {
+        ok(false, 'addTransceiver("foo") throws a TypeError');
+      }
     }
 
     hasProps(pc.getTransceivers(), []);