[FIX] to_backend_theme: Fix pad UI goes wrong

- Currently in Chrome, parent-flex not having a true value so when
flex-basis apply, the child don't know what size to compute when size of
parent changed. It makes the editor shrink to much and user can not use
this editor
This PR will fix this problem.

Author: Ngquang

to_backend_theme/static/src/scss/style.scss

@@ -70,6 +70,7 @@ body {
 	}
 }
 
+// Avoid avatar image strech
 .o_Follower{
     a{
         .o_Follower_avatar{
@@ -78,6 +79,26 @@ body {
     }
 }
 
+// Fix chrome not filling percentage% height of flex parent
+.o_note_form_view.o_form_view {
+    .o_form_sheet_bg {
+        // Odoo try to set a child height with true value (500px) but the correctly way is set true value for parent-flex
+        // currently Odoo set .oe_pad .oe_pad_content.oe_editing {height:500px; ...}
+        height: 500px;
+        .o_form_sheet {
+            .oe_pad {
+                .oe_pad_content {
+                    display: flex;
+                }
+            }    
+        }
+    }
+}
+.oe_pad .oe_pad_content.oe_editing{
+    display: flex;
+    flex: 1;
+}
+
 .o_control_panel {
 	.o_cp_right {
 		.btn-secondary {