Work on major sub-task EXT-991 (Update bottom bar behavior on resize)

Improved functionality to process Buttons showing via context menu
 - added new alert dialog ("BottomTrayButtonCanNotBeShown") in case when there is no enough space to show button

For now it contains a such message:
"Selected button can not be shown right now.
The button will be shown when there is enough space for it."

It should be reviewed by XUI team

--HG--
branch : product-engine

indra/newview/llbottomtray.cpp

@@ -761,6 +761,7 @@ void LLBottomTray::setTrayButtonVisibleIfPossible(EResizeState shown_object_type
 	{
 		// mark this button to show it while future bottom tray extending
 		mResizeState |= shown_object_type;
+		LLNotifications::instance().add("BottomTrayButtonCanNotBeShown");
 	}
 }
 

indra/newview/skins/default/xui/en/notifications.xml

@@ -5739,6 +5739,15 @@ Are you sure you want to delete your teleport history?
      yestext="OK"/>
   </notification>
 
+  <notification
+   icon="alert.tga"
+   name="BottomTrayButtonCanNotBeShown"
+   type="alert">
+Selected button can not be shown right now.
+The button will be shown when there is enough space for it.
+  </notification>
+
+
   <global name="UnsupportedCPU">
 - Your CPU speed does not meet the minimum requirements.
   </global>