Add default error handler to remote promises (#6151)

* Add failing spec for unhandled main process exception

* Remove unused return

* Use let/const instead of var

* Add spec for unhandled rejection in renderer process

* Prevent unhandled rejection defaul

* Use once instead of on

* Add default fulfilled/rejection handler to promise

spec/api-ipc-spec.js

@@ -126,6 +126,33 @@ describe('ipc module', function () {
         done()
       })
     })
+
+    it('does not emit unhandled rejection events in the main process', function (done) {
+      remote.process.once('unhandledRejection', function (reason) {
+        done(reason)
+      })
+
+      var promise = remote.require(path.join(fixtures, 'module', 'unhandled-rejection.js'))
+      promise.reject().then(function () {
+        done(new Error('Promise was not rejected'))
+      }).catch(function (error) {
+        assert.equal(error.message, 'rejected')
+        done()
+      })
+    })
+
+    it('emits unhandled rejection events in the renderer process', function (done) {
+      window.addEventListener('unhandledrejection', function (event) {
+        event.preventDefault()
+        assert.equal(event.reason.message, 'rejected')
+        done()
+      })
+
+      var promise = remote.require(path.join(fixtures, 'module', 'unhandled-rejection.js'))
+      promise.reject().then(function () {
+        done(new Error('Promise was not rejected'))
+      })
+    })
   })
 
   describe('remote webContents', function () {