[epiphany/mcatanzaro/thumbnail-background-position] Make overview thumbnail bcakground-size idempotent

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 787c42d929be406411f8cfc11e8042ebec8e95f9
Author: Michael Catanzaro <mcatanzaro gnome org>
Date:   Tue Aug 6 12:35:23 2019 -0500

    Make overview thumbnail bcakground-size idempotent
    
    This should have no effect because we should never transition from a
    placeholder thumbnail to a web snapshot, but it's certainly more robust.

 embed/web-process-extension/resources/js/overview.js | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/embed/web-process-extension/resources/js/overview.js 
b/embed/web-process-extension/resources/js/overview.js
index eaab98dd7..df65a6272 100644
--- a/embed/web-process-extension/resources/js/overview.js
+++ b/embed/web-process-extension/resources/js/overview.js
@@ -243,6 +243,7 @@ Ephy.Overview.Item = class OverviewItem
             this._thumbnail.style.backgroundPosition = 'top';
         } else {
             this._thumbnail.style.backgroundImage = '';
+            this._thumbnail.style.backgroundSize = 'auto';
             this._thumbnail.style.backgroundPosition = 'center';
         }
     }