[FIX] mail: nocontent helper discuss (inbox & starred)

Revision on https://github.com/odoo/odoo/commit/a87d761fdbf345ada5dc93e0a686b08a0f5a0417

From the UX/UI changes above, we also changed the style for empty
inbox and starred in Discuss.

There are two issues with the empty boxes message:

    1. The text is not centered at all (one word per line,
       and everything is stuck on the left-side of the screen)
    2. The style is inconsistent with nocontent message on search

In this commit, inbox and starred use the same style as the no_content
message from a search. The style of the nocontent from a search has been
slightly changed to mimick the intended style for inbox and starred:

    - centered text
    - title is in bold 125% font size
    - other text is not in bold, 115% font size.

4 files changed, 17 insertions, 23 deletions

diff --git a/addons/mail/static/src/less/discuss.less b/addons/mail/static/src/less/discuss.less
index a90d0df94bd..02e041cac02 100644
--- a/addons/mail/static/src/less/discuss.less
+++ b/addons/mail/static/src/less/discuss.less
@@ -321,15 +321,11 @@
 
         .o_mail_chat_content {
             .o-flex(1, 0, 0);
-            margin-left: 0;
+            margin-left: 10px;
+            margin-right: 10px;
             background-color: transparent;
-            .o_mail_no_content {
-                .o-position-absolute(@top: 30%);
-                text-align: center;
-            }
         }
 
-
         .o_mail_chat_tab_pane {
             overflow-x: scroll;
             .o_mail_add_channel {
diff --git a/addons/mail/static/src/less/thread.less b/addons/mail/static/src/less/thread.less
index 8d8bc761829..81dee297011 100644
--- a/addons/mail/static/src/less/thread.less
+++ b/addons/mail/static/src/less/thread.less
@@ -208,11 +208,14 @@
     .o_thread_title {
         margin-top: 20px;
         margin-bottom: 20px;
-        font-size: 20px;
+        font-weight: bold;
+        font-size: 125%;
     }
 
     .o_mail_no_content {
-        .o-webclient-padding();
+        .o-position-absolute(30%, 0, 0, 0);
+        text-align: center;
+        font-size: 115%;
     }
 
     .o_thread_message .o_thread_message_core .o_mail_read_more {
diff --git a/addons/mail/static/src/xml/thread.xml b/addons/mail/static/src/xml/thread.xml
index b5f8a1c7849..26c093c3e84 100644
--- a/addons/mail/static/src/xml/thread.xml
+++ b/addons/mail/static/src/xml/thread.xml
@@ -110,18 +110,14 @@
 
     <!-- When a channel is empty-->
     <div t-name="mail.EmptyChannel" class="o_mail_no_content">
-        <div class="o_view_nocontent">
-            <div class="o_nocontent_help">
-                <t t-if="options.channel_id==='channel_inbox'">
-                    <p>Congratulations, your inbox is empty</p>
-                    <p>New messages appear here.</p>
-                </t>
-                <t t-if="options.channel_id==='channel_starred'">
-                    <p>No starred message</p>
-                    <p>You can mark any message as 'starred', and it shows up in this channel.</p>
-                </t>
-            </div>
-        </div>
+        <t t-if="options.channel_id==='channel_inbox'">
+            <div class="o_thread_title">Congratulations, your inbox is empty</div>
+            <div>New messages appear here.</div>
+        </t>
+        <t t-if="options.channel_id==='channel_starred'">
+            <div class="o_thread_title">No starred message</div>
+            <div>You can mark any message as 'starred', and it shows up in this channel.</div>
+        </t>
     </div>
 
     <t t-name="mail.ChatThread.Content">
diff --git a/addons/mail/static/tests/discuss_tests.js b/addons/mail/static/tests/discuss_tests.js
index 4338db1cfaf..6990a04efba 100644
--- a/addons/mail/static/tests/discuss_tests.js
+++ b/addons/mail/static/tests/discuss_tests.js
@@ -44,10 +44,9 @@ QUnit.test('basic rendering', function (assert) {
         assert.strictEqual($sidebar.length, 1,
             "should have rendered a sidebar");
 
-        var $nocontent = discuss.$('.o_mail_chat_content');
-        assert.strictEqual($nocontent.length, 1,
+        assert.strictEqual(discuss.$('.o_mail_chat_content').length, 1,
             "should have rendered the content");
-        assert.strictEqual($nocontent.find('.o_mail_no_content').length, 1,
+        assert.strictEqual(discuss.$('.o_mail_no_content').length, 1,
             "should display no content message");
 
         var $inbox = $sidebar.find('.o_mail_chat_channel_item[data-channel-id=channel_inbox]');