Bug 1581418 - Include more properties when logging objects, r=jlast.

Differential Revision: https://phabricator.services.mozilla.com/D45961

devtools/shared/DevToolsUtils.js

@@ -887,6 +887,12 @@ errorOnFlag(exports, "wantVerbose");
 // where unsafeDereference will return an opaque security wrapper to the
 // referent.
 function callPropertyOnObject(object, name, ...args) {
+  // When replaying, the result of the call may already be known, which avoids
+  // having to communicate with the replaying process.
+  if (isReplaying && args.length == 0 && object.replayHasCallResult(name)) {
+    return object.replayCallResult(name);
+  }
+
   // Find the property.
   let descriptor;
   let proto = object;