[REF] *: get rid of introduced @​extend

During first scss convertion, classes called as mixins were changed to
an @​extend instruction which was the best approximation given the fact
there is no equivalent in sass to do that. The problem is that the
instruction is slowing the scss computation a lot and might also break
the style in unexpected ways because of the complex unwanted selectors
the instruction induces.

This commit removes the need of extends. This is done case per case.
Sometimes this involves adding classes in xml, sometimes to change the
style a little, ... The button rendering refactoring which was made
at the start of the LESS to SASS merge was also done in prevision of
this.

After this commit, sass computation is like 5-6 times faster than less
computation while it was like 10 times *slower* before this commit.

5 files changed, 11 insertions, 22 deletions

diff --git a/addons/web/static/src/scss/dropdown_extra.scss b/addons/web/static/src/scss/dropdown_extra.scss
index f925c4f6190..d15496fe0c9 100644
--- a/addons/web/static/src/scss/dropdown_extra.scss
+++ b/addons/web/static/src/scss/dropdown_extra.scss
@@ -56,8 +56,3 @@ $tag-border: #afafb6;
         }
     }
 }
-
-// Buttons used as dropdown toggler
-.o_dropdown_toggler_btn {
-    @extend .btn-default; // FIXME was a mixin before scss convertion
-}
diff --git a/addons/web/static/src/scss/form_view.scss b/addons/web/static/src/scss/form_view.scss
index 3698ee07e74..c5e0207022d 100644
--- a/addons/web/static/src/scss/form_view.scss
+++ b/addons/web/static/src/scss/form_view.scss
@@ -3,7 +3,6 @@
 
     // Utility classes
     .oe_form_box_info {
-        @extend .bg-info; // FIXME was a mixin before scss convertion
         @include o-webclient-padding($top: 5px, $bottom: 5px);
         > p {
             margin: auto;
@@ -24,11 +23,11 @@
         }
     }
     .oe_left {
-        @extend .oe_inline; // FIXME was a mixin before scss convertion
+        @extend .oe_inline;
         float: left!important;
     }
     .oe_right {
-        @extend .oe_inline; // FIXME was a mixin before scss convertion
+        @extend .oe_inline;
         float: right!important;
     }
 
@@ -443,7 +442,7 @@
 
     // Specific style classes
     .o_group.o_inner_group.oe_subtotal_footer {
-        @extend .oe_right; // FIXME was a mixin after scss convertion
+        @extend .oe_right;
 
         > tbody > tr > td {
             padding: 0;
diff --git a/addons/web/static/src/scss/kanban_dashboard.scss b/addons/web/static/src/scss/kanban_dashboard.scss
index 0a1688260a8..791b582efd1 100644
--- a/addons/web/static/src/scss/kanban_dashboard.scss
+++ b/addons/web/static/src/scss/kanban_dashboard.scss
@@ -209,7 +209,6 @@ $o-kanban-dashboard-dropdown-complex-gap: 5px;
         }
 
         .o_kanban_card_manage_pane {
-            @extend .dropdown-menu; // FIXME was a mixin before scss convertion
             @include o-kanban-dropdown-menu;
 
             // Arbitrary value to place the dropdown-menu exactly below the
@@ -252,8 +251,11 @@ $o-kanban-dashboard-dropdown-complex-gap: 5px;
                     padding-right: $o-kanban-dashboard-dropdown-complex-gap;
 
                     > .o_kanban_card_manage_title {
-                        @extend .h5; // FIXME was a mixin before scss convertion
+                        margin: ($line-height-computed / 2) 0;
+                        color: $headings-color;
+                        font-size: $font-size-h5;
                         font-weight: 500;
+                        line-height: $headings-line-height;
                     }
                     > div:not(.o_kanban_card_manage_title) {
                         @include o-kanban-dashboard-dropdown-link($link-padding-gap: $o-kanban-dashboard-dropdown-complex-gap);
diff --git a/addons/web/static/src/scss/search_view_extra.scss b/addons/web/static/src/scss/search_view_extra.scss
index e5b378e6e41..247b188c396 100644
--- a/addons/web/static/src/scss/search_view_extra.scss
+++ b/addons/web/static/src/scss/search_view_extra.scss
@@ -34,10 +34,3 @@
         }
     }
 }
-
-// Search options: inputs and selects style
-.o_search_options {
-    input[type="text"], select {
-        @extend .form-control; // FIXME was a mixin before scss convertion
-    }
-}
diff --git a/addons/web/static/src/xml/base.xml b/addons/web/static/src/xml/base.xml
index 44412379a93..957e5ce6953 100644
--- a/addons/web/static/src/xml/base.xml
+++ b/addons/web/static/src/xml/base.xml
@@ -318,7 +318,7 @@
 <t t-name="Sidebar">
     <t t-foreach="widget.sections" t-as="section">
         <div class="btn-group o_dropdown">
-            <button t-if="section.name != 'buttons'" class="o_dropdown_toggler_btn btn btn-sm dropdown-toggle" data-toggle="dropdown" aria-expanded="false">
+            <button t-if="section.name != 'buttons'" class="o_dropdown_toggler_btn btn btn-sm btn-link btn-default dropdown-toggle" data-toggle="dropdown" aria-expanded="false">
                 <t t-if="section.name == 'files'" t-raw="widget.items[section.name].length || ''"/>
                 <t t-esc="section.label"/> <span class="caret"/>
             </button>
@@ -1026,7 +1026,7 @@
     <ul class="dropdown-menu o_searchview_autocomplete" role="menu"></ul>
 </t>
 <div t-name="SearchView.FilterMenu" class="btn-group o_dropdown">
-    <button class="o_dropdown_toggler_btn btn btn-sm dropdown-toggle" data-toggle="dropdown" aria-expanded="false" tabindex="-1">
+    <button class="o_dropdown_toggler_btn btn btn-sm btn-link btn-default dropdown-toggle" data-toggle="dropdown" aria-expanded="false" tabindex="-1">
         <span class="fa fa-filter"/> Filters <span class="caret"/>
     </button>
     <ul class="dropdown-menu o_filters_menu" role="menu">
@@ -1138,7 +1138,7 @@
     </select>
 </t>
 <div t-name="SearchView.GroupByMenu" class="btn-group hidden-xs o_dropdown">
-    <button class="o_dropdown_toggler_btn btn btn-sm dropdown-toggle" data-toggle="dropdown" aria-expanded="false" tabindex="-1">
+    <button class="o_dropdown_toggler_btn btn btn-sm btn-link btn-default dropdown-toggle" data-toggle="dropdown" aria-expanded="false" tabindex="-1">
         <span class="fa fa-bars"/> Group By <span class="caret"/>
     </button>
     <ul class="dropdown-menu o_group_by_menu" role="menu">
@@ -1159,7 +1159,7 @@
     </li>
 </t>
 <div t-name="SearchView.FavoriteMenu" class="btn-group o_dropdown">
-    <button class="o_dropdown_toggler_btn btn btn-sm dropdown-toggle" data-toggle="dropdown" aria-expanded="false" tabindex="-1">
+    <button class="o_dropdown_toggler_btn btn btn-sm btn-link btn-default dropdown-toggle" data-toggle="dropdown" aria-expanded="false" tabindex="-1">
         <span class="fa fa-star"/> Favorites <span class="caret"/>
     </button>
     <ul class="dropdown-menu o_favorites_menu" role="menu">