[gnome-builder] html preview: prevent multiple preview opening

[Sébastien Lafargue <slafargue src gnome org>]

commit 31e2c6d074e4c34377ead715e06f9c9190954f64
Author: Sebastien Lafargue <slafargue gnome org>
Date:   Sun Mar 26 16:31:49 2017 +0200

    html preview: prevent multiple preview opening

 .../html-preview/html_preview_plugin/__init__.py   |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/plugins/html-preview/html_preview_plugin/__init__.py 
b/plugins/html-preview/html_preview_plugin/__init__.py
index 5b51a4f..bd8fc7c 100644
--- a/plugins/html-preview/html_preview_plugin/__init__.py
+++ b/plugins/html-preview/html_preview_plugin/__init__.py
@@ -273,6 +273,12 @@ class HtmlPreviewAddin(GObject.Object, Ide.EditorViewAddin):
         stack = view.get_ancestor(Ide.LayoutStack)
         stack.add(web_view)
 
+        self.action.set_enabled(False)
+        web_view.connect('destroy', lambda *_: self.web_view_destroyed(web_view))
+
+    def web_view_destroyed(self, web_view):
+        self.action.set_enabled(True)
+
     def search_sphinx_base_dir(self, path):
         context = self.workbench.get_context()
         vcs = context.get_vcs()