promise-valued.patch

diff --git a/devtools/server/actors/object.js b/devtools/server/actors/object.js
--- a/devtools/server/actors/object.js
+++ b/devtools/server/actors/object.js
@@ -397,17 +397,22 @@ ObjectActor.prototype = {
           obj._safeGetters = null;
           continue;
         }
 
         let result = getter.call(this.obj);
         if (result && !("throw" in result)) {
           let getterValue = undefined;
           if ("return" in result) {
-            getterValue = result.return;
+            // Promise-returning getters always return a promise; but it might be rejected.
+            // treat that as if the call threw an exception.
+            if (!(result.return.isPromise &&
+                  result.return.promiseState === "rejected")) {
+              getterValue = result.return;
+            }
           } else if ("yield" in result) {
             getterValue = result.yield;
           }
           // WebIDL attributes specified with the LenientThis extended attribute
           // return undefined and should be ignored.
           if (getterValue !== undefined) {
             safeGetterValues[name] = {
               getterValue: this.hooks.createValueGrip(getterValue),