Bug 1254865 - Set disableglobalhistory on the thumbnail browser. r=Felipe

MozReview-Commit-ID: 9SXEAo0H0ko

--HG--
extra : rebase_source : 547d6492d1b3e93998b90f8a19923933ca2c33c2

toolkit/components/thumbnails/BackgroundPageThumbs.jsm

@@ -171,6 +171,7 @@ const BackgroundPageThumbs = {
     let browser = this._parentWin.document.createElementNS(XUL_NS, "browser");
     browser.setAttribute("type", "content");
     browser.setAttribute("remote", "true");
+    browser.setAttribute("disableglobalhistory", "true");
 
     // Size the browser.  Make its aspect ratio the same as the canvases' that
     // the thumbnails are drawn into; the canvases' aspect ratio is the same as