Avoid timing issues with polyfilled Promise

Author: kevinpschaaf

test/unit/path-effects.html

@@ -106,7 +106,7 @@
         assert.equal(el.$.forward.$.compose.objSubpathChanged.firstCall.args[0].path, 'obj');
         assert.equal(el.$.forward.$.compose.objSubpathChanged.firstCall.args[0].value, nested.obj);
         // x-pe uses async PropertiesChanged
-        Promise.resolve().then(() => {
+        setTimeout(() => {
           assert.equal(el.$.pe._propertiesChanged.callCount, 1);
           assert.equal(el.$.pe._propertiesChanged.firstCall.args[1].obj, nested.obj);
           done();
@@ -124,7 +124,7 @@
         assert.equal(el.$.forward.$.compose.objSubpathChanged.firstCall.args[0].path, 'obj');
         assert.equal(el.$.forward.$.compose.objSubpathChanged.firstCall.args[0].value, nested.obj);
         // x-pe uses async PropertiesChanged
-        Promise.resolve().then(() => {
+        setTimeout(() => {
           assert.equal(el.$.pe._propertiesChanged.callCount, 1);
           assert.equal(el.$.pe._propertiesChanged.firstCall.args[1].obj, nested.obj);
           done();
@@ -142,7 +142,7 @@
         assert.equal(el.$.forward.$.compose.objSubpathChanged.firstCall.args[0].path, 'obj.value');
         assert.equal(el.$.forward.$.compose.objSubpathChanged.firstCall.args[0].value, 42);
         // x-pe uses async PropertiesChanged
-        Promise.resolve().then(() => {
+        setTimeout(() => {
           // Note the PropertiesMixin element only sees a deep set to 'nested.obj.value'
           // because it overrides _shouldPropertyChange to allow object re-sets through
           assert.equal(el.$.pe._propertiesChanged.callCount, 1);