[geary] Ensure embedded composer is always scrolled to when opened.

[Michael Gratton <mjog src gnome org>]

commit 101075d1ed62a5e2084ab3321ff62639aa857ccc
Author: Michael James Gratton <mike vee net>
Date:   Tue Apr 17 12:34:48 2018 +1000

    Ensure embedded composer is always scrolled to when opened.
    
    Fixes Bug 778027.
    
    * src/client/conversation-viewer/conversation-viewer.vala
      (ConversationViewer): Disable disable kinetic scrolling before showing
      an embedded composer so that if it still has some momentum when the
      composer is inserted and scrolled to, it won't jump away again.

 .../conversation-viewer/conversation-viewer.vala   |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)
---
diff --git a/src/client/conversation-viewer/conversation-viewer.vala 
b/src/client/conversation-viewer/conversation-viewer.vala
index 7fde896..8e92a51 100644
--- a/src/client/conversation-viewer/conversation-viewer.vala
+++ b/src/client/conversation-viewer/conversation-viewer.vala
@@ -145,9 +145,16 @@ public class ConversationViewer : Gtk.Stack, Geary.BaseInterface {
             this.conversation_scroller
         );
 
+        // We need to disable kinetic scrolling so that if it still
+        // has some momentum when the composer is inserted and
+        // scrolled to, it won't jump away again. See Bug 778027.
+        conversation_scroller.kinetic_scrolling = false;
+
         if (this.current_list != null) {
             this.current_list.add_embedded_composer(embed, is_draft);
         }
+
+        conversation_scroller.kinetic_scrolling = true;
     }
 
     /**