Bug 1267501: Adjust hardcoded 'width' in new Private Browsing UI to be a max-width instead, so it fits better in skinny windows. r=rickychien

MozReview-Commit-ID: 3CZP0sg9nZh

--HG--
extra : rebase_source : daffb94ff7cfbbf6aed264817fcbd48b36777abc

browser/themes/shared/privatebrowsing/aboutPrivateBrowsing.css

@@ -52,7 +52,7 @@ a:visited {
 }
 
 .about-content-container {
-  width: 780px;
+  max-width: 780px;
 }
 
 section.section-main {