SIP-32: Moving frontend code to the base of the repo (#9098)

* move assets out, get webpack dev working

* update docs to reference superset-frontend

* draw the rest of the owl

* fix docs

* fix webpack script

* rats

* correct docs

* fix tox dox

superset-frontend/src/utils/DebouncedMessageQueue.js

@@ -0,0 +1,51 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+import { debounce } from 'lodash';
+
+class DebouncedMessageQueue {
+  constructor({
+    callback = () => {},
+    sizeThreshold = 1000,
+    delayThreshold = 1000,
+  }) {
+    this.queue = [];
+    this.sizeThreshold = sizeThreshold;
+    this.delayThrehold = delayThreshold;
+
+    this.trigger = debounce(this.trigger.bind(this), this.delayThrehold);
+    this.callback = callback;
+  }
+  append(eventData) {
+    this.queue.push(eventData);
+    this.trigger();
+  }
+  trigger() {
+    if (this.queue.length > 0) {
+      const events = this.queue.splice(0, this.sizeThreshold);
+      this.callback.call(null, events);
+
+      // If there are remaining items, call it again.
+      if (this.queue.length > 0) {
+        this.trigger();
+      }
+    }
+  }
+}
+
+export default DebouncedMessageQueue;