[FIX] mail: prevent race condition in client action

The issue was that the chat_manager was an async js module, so it could
be loaded quite late.  Then the client action was loaded only after the
chat_manager was ready, and possibly before the action_manager read the
value in the action registry.

This commits prevent this problem from happening by turning the chat
manager into a sync module, so the chatter and the client action needs
to wait for him to be ready before doing their magic.

addons/mail/static/src/js/chat_manager.js

@@ -524,10 +524,11 @@ function init () {
             action_id: action_id,
         };
         bus.start_polling();
-        return chat_manager;
     });
 }
 
-return init();
+chat_manager.is_ready = init();
+
+return chat_manager;
 
 });

addons/mail/static/src/js/chatter.js

@@ -12,7 +12,6 @@ var data = require('web.data');
 var Dialog = require('web.Dialog');
 var form_common = require('web.form_common');
 var session = require('web.session');
-var web_client = require('web.web_client');
 
 var _t = core._t;
 var qweb = core.qweb;
@@ -696,6 +695,10 @@ var Chatter = form_common.AbstractField.extend({
         this.context = this.options.context || {};
     },
 
+    willStart: function () {
+        return chat_manager.is_ready;
+    },
+
     start: function () {
         var self = this;
 

addons/mail/static/src/js/client_action.js

@@ -127,6 +127,10 @@ var ChatAction = Widget.extend(ControlPanelMixin, {
         this.channels_scrolltop = {};
     },
 
+    willStart: function () {
+        return chat_manager.is_ready;
+    },
+
     start: function() {
         var self = this;
 

addons/mail/static/src/js/window_manager.js

@@ -106,10 +106,12 @@ core.bus.on('web_client_ready', null, function () {
         });
     });
 
-    _.each(chat_manager.get_channels(), function (channel) {
-        if (channel.is_detached) {
-            open_chat(channel);
-        }
+    chat_manager.is_ready.then(function() {
+        _.each(chat_manager.get_channels(), function (channel) {
+            if (channel.is_detached) {
+                open_chat(channel);
+            }
+        });
     });
 });