Added timer to explore v2 and share it with sqllab (#1802)

* Added timer to explore v2 and share it with sqllab

* Fixed js tests

* Add timer to initial load

* Make timer smaller

* nits

superset/assets/javascripts/explorev2/reducers/exploreReducer.js

@@ -1,6 +1,7 @@
 import { defaultFormData } from '../stores/store';
 import * as actions from '../actions/exploreActions';
 import { addToArr, removeFromArr, alterInArr } from '../../../utils/reducerUtils';
+import { now } from '../../modules/dates';
 
 export const exploreReducer = function (state, action) {
   const actionHandlers = {
@@ -113,19 +114,32 @@ export const exploreReducer = function (state, action) {
         query: action.viz.query,
         data: action.viz.data,
       };
+      const chartUpdateEndTime = now();
       return Object.assign(
         {},
         state,
         {
           viz: Object.assign({}, state.viz, vizUpdates),
-          isChartLoading: false,
+          chartStatus: 'success',
+          chartUpdateEndTime,
         });
     },
     [actions.CHART_UPDATE_STARTED]() {
-      return Object.assign({}, state, { isChartLoading: true });
+      const chartUpdateStartTime = now();
+      return Object.assign({}, state,
+        { chartStatus: 'loading', chartUpdateEndTime: null, chartUpdateStartTime });
     },
     [actions.CHART_UPDATE_FAILED]() {
-      return Object.assign({}, state, { isChartLoading: false, chartAlert: action.error });
+      const chartUpdateEndTime = now();
+      return Object.assign({}, state,
+        { chartStatus: 'failed', chartAlert: action.error, chartUpdateEndTime });
+    },
+    [actions.UPDATE_CHART_STATUS]() {
+      const newState = Object.assign({}, state, { chartStatus: action.status });
+      if (action.status === 'success' || action.status === 'failed') {
+        newState.chartUpdateEndTime = now();
+      }
+      return newState;
     },
     [actions.REMOVE_CHART_ALERT]() {
       return Object.assign({}, state, { chartAlert: null });