Bug 1399499 - Add additional margin-top to the tabs toolbar on Windows 7 per Photon spec. r=nhnt11

MozReview-Commit-ID: E3lWYq29eTQ

--HG--
extra : rebase_source : db3171195b998a6988c832615e00589614b20f49

browser/themes/windows/browser.css

@@ -78,6 +78,14 @@
   margin-top: var(--space-above-tabbar);
 }
 
+/* Add 4px extra margin on top of the tabs toolbar on Windows 7. */
+@media (-moz-os-version: windows-win7) {
+  :root[sizemode="normal"][chromehidden~="menubar"] #toolbar-menubar ~ #TabsToolbar,
+  :root[sizemode="normal"] #toolbar-menubar[autohide="true"][inactive] ~ #TabsToolbar {
+    margin-top: calc(var(--space-above-tabbar) + 4px);
+  }
+}
+
 #navigator-toolbox,
 #navigator-toolbox > toolbar {
   -moz-appearance: none;