diff --git a/static_src/reducers/base.js b/static_src/reducers/base.js
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+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import {connect} from 'pwa-helpers/connect-mixin.js';
+import {applyMiddleware, combineReducers, compose, createStore} from 'redux';
+import thunk from 'redux-thunk';
+import {hotlists} from './hotlists.js';
+import * as issueV0 from './issueV0.js';
+import * as permissions from './permissions.js';
+import * as projects from './projects.js';
+import * as projectV0 from './projectV0.js';
+import * as sitewide from './sitewide.js';
+import {stars} from './stars.js';
+import * as users from './users.js';
+import * as userV0 from './userV0.js';
+import * as ui from './ui.js';
+
+/** @typedef {import('redux').AnyAction} AnyAction */
+
+// Actions
+const RESET_STATE = 'RESET_STATE';
+
+/* State Shape
+{
+  hotlists: Object,
+  permissions: Object,
+  projects: Object,
+  sitewide: Object,
+  users: Object,
+
+  ui: Object,
+
+  // To be deprecated
+  issue: Object,
+  projectV0: Object,
+  userV0: Object,
+}
+*/
+
+// Reducers
+const reducer = combineReducers({
+  hotlists: hotlists.reducer,
+  issue: issueV0.reducer,
+  permissions: permissions.reducer,
+  projects: projects.reducer,
+  projectV0: projectV0.reducer,
+  users: users.reducer,
+  userV0: userV0.reducer,
+  sitewide: sitewide.reducer,
+  stars: stars.reducer,
+
+  ui: ui.reducer,
+});
+
+/**
+ * The top level reducer function that all actions pass through.
+ * @param {any} state
+ * @param {AnyAction} action
+ * @return {any}
+ */
+export function rootReducer(state, action) {
+  if (action.type === RESET_STATE) {
+    state = undefined;
+  }
+  return reducer(state, action);
+}
+
+// Selectors
+
+// Action Creators
+
+/**
+ * Changes Redux state back to its default initial state. Primarily
+ * used in testing.
+ * @return {AnyAction} An action to reset Redux state to default.
+ */
+export const resetState = () => ({type: RESET_STATE});
+
+// Store
+
+// For debugging with the Redux Devtools extension:
+// https://chrome.google.com/webstore/detail/redux-devtools/lmhkpmbekcpmknklioeibfkpmmfibljd/
+const composeEnhancers = window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__ || compose;
+export const store = createStore(rootReducer, composeEnhancers(
+    applyMiddleware(thunk),
+));
+
+/**
+ * Class mixin function that connects a given HTMLElement class to our
+ * store instance.
+ * @link https://pwa-starter-kit.polymer-project.org/redux-and-state-management#connecting-an-element-to-the-store
+ * @param {typeof HTMLElement} class
+ * @return {function} New class type with connected features.
+ */
+export const connectStore = connect(store);
+
+/**
+ * Promise to allow waiting for a state update. Useful in testing.
+ * @example
+ * store.dispatch(updateState());
+ * await stateUpdated;
+ * doThingWithUpdatedState();
+ *
+ * @type {Promise}
+ */
+export const stateUpdated = new Promise((resolve) => {
+  store.subscribe(resolve);
+});