Delete string at view level and add to ir.model.button.

Add icon attribute to cls._buttons on model.

activity.py

@@ -40,8 +40,12 @@ class Activity(metaclass=PoolMeta):
     def __setup__(cls):
         super(Activity, cls).__setup__()
         cls._buttons.update({
-            'new': {},
-            'reply': {},
+            'new': {
+                'icon': 'tryton-email',
+            },
+            'reply': {
+                'icon': 'tryton-forward'
+            },
             })
 
     @property

activity.xml

@@ -22,7 +22,7 @@
 
         <record model="ir.model.button" id="electronic_mail_new_button">
             <field name="name">new</field>
-            <field name="string">New</field>
+            <field name="string">Send Mail</field>
             <field name="model" search="[('model', '=', 'activity.activity')]"/>
         </record>
         <record model="ir.model.button-res.group"
@@ -33,7 +33,7 @@
 
         <record model="ir.model.button" id="electronic_mail_reply_button">
             <field name="name">reply</field>
-            <field name="string">Reply</field>
+            <field name="string">Reply Mail</field>
             <field name="model" search="[('model', '=', 'activity.activity')]"/>
         </record>
         <record model="ir.model.button-res.group"

view/activity_activity_form.xml

@@ -10,8 +10,8 @@
             <label name="mail" />
             <field name="mail" />
             <group colspan="2" col="2" id="buttons">
-                <button name="new" string="Send Mail" icon="tryton-email"/>
-                <button name="reply" string="Reply Mail" icon="tryton-forward"/>
+                <button name="new"/>
+                <button name="reply"/>
                 <field name="have_mail" invisible="1"/>
             </group>
         </group>

view/activity_activity_tree.xml

@@ -3,8 +3,8 @@
      copyright notices and license terms. -->
 <data>
     <xpath expr="/tree/field[@name='state']" position="after">
-        <button name="new" string="Send Mail"/>
-        <button name="reply" string="Reply Mail"/>
+        <button name="new"/>
+        <button name="reply"/>
         <field name="have_mail" tree_invisible="1"/>
     </xpath>
 </data>