Replace deprecated render(buffer) with a custom buffered renderer

app/assets/javascripts/discourse-common/lib/buffered-render.js.es6

@@ -0,0 +1,53 @@
+// Ember 2.0 removes buffered rendering, but we can still implement it ourselves.
+// In the long term we'll want to remove this.
+
+const Mixin = {
+  __bufferTimeout: null,
+
+  _customRender() {
+    Ember.run.cancel(this.__bufferTimeout);
+    if (!this.element || this.isDestroying || this.isDestroyed) { return; }
+
+    const buffer = [];
+    this.buildBuffer(buffer);
+    this.element.innerHTML = buffer.join('');
+  },
+
+  rerenderBuffer() {
+    Ember.run.scheduleOnce('render', this, this._customRender);
+  }
+};
+
+export function bufferedRender(obj) {
+
+  if (!obj.buildBuffer) {
+    Ember.warn('Missing `buildBuffer` method');
+    return obj;
+  }
+
+  const caller = {};
+
+  // True in 1.13 or greater
+  if (Ember.Helper) {
+    caller.didRender = function() {
+      this._super();
+      this._customRender();
+    };
+  } else {
+    caller.didInsertElement = function() {
+      this._super();
+      this._customRender();
+    };
+  }
+
+  const triggers = obj.rerenderTriggers;
+  if (triggers) {
+    caller.init = function() {
+      this._super();
+      triggers.forEach(k => this.addObserver(k, this.rerenderBuffer));
+    };
+  }
+  delete obj.rerenderTriggers;
+
+  return Ember.Mixin.create(Mixin, caller, obj);
+}