--- a/browser/base/content/browser-tabsintitlebar.js
+++ b/browser/base/content/browser-tabsintitlebar.js
@@ -226,17 +226,36 @@ var TabsInTitlebar = {
       // Next, we calculate how much we need to stretch the titlebar down to
       // go all the way to the bottom of the tab strip, if necessary.
       let tabAndMenuHeight = fullTabsHeight + fullMenuHeight;
 
       if (tabAndMenuHeight > titlebarContentHeight) {
         // We need to increase the titlebar content's outer height (ie including margins)
         // to match the tab and menu height:
         let extraMargin = tabAndMenuHeight - titlebarContentHeight;
-        if (AppConstants.platform != "macosx") {
+        if (AppConstants.platform == "linux") {
+          // Linux centers buttons at titlebar so let's emulate that.
+          if (!fullMenuHeight) {
+            // Menubar is not visible - center buttons according to tabs.
+            titlebarContent.style.marginTop = extraMargin/2 + "px";
+            titlebarContent.style.marginBottom = extraMargin/2 + "px";
+          } else {
+            if (fullMenuHeight > titlebarContentHeight) {
+              // Buttons are smaller than menubar so center them according to menubar.
+              let fullMenuHeightMargin = fullMenuHeight - titlebarContentHeight;
+              titlebarContent.style.marginTop = fullMenuHeightMargin/2 + "px";
+              titlebarContent.style.marginBottom = fullMenuHeightMargin/2 + (extraMargin - fullMenuHeightMargin) + "px";
+            } else {
+              // Buttons are bigger than menubar - place them at top with some
+              // reasonable top margin.
+              titlebarContent.style.marginTop = "2px";
+              titlebarContent.style.marginBottom = extraMargin - 2 + "px";
+            }
+          }
+        } else if (AppConstants.platform != "macosx") {
           titlebarContent.style.marginBottom = extraMargin + "px";
         }
 
         titlebarContentHeight += extraMargin;
       } else {
         titlebarContent.style.removeProperty("margin-bottom");
       }
 

--- a/widget/gtk/gtk3drawing.cpp
+++ b/widget/gtk/gtk3drawing.cpp
@@ -2366,16 +2366,17 @@ moz_gtk_get_widget_border(WidgetNodeType
 
             return MOZ_GTK_SUCCESS;
         }
     case MOZ_GTK_HEADER_BAR:
     case MOZ_GTK_HEADER_BAR_MAXIMIZED:
         {
             style = GetStyleContext(widget);
             moz_gtk_add_border_padding(style, left, top, right, bottom);
+            *top = *bottom = 0;
             return MOZ_GTK_SUCCESS;
         }
     /* These widgets have no borders, since they are not containers. */
     case MOZ_GTK_CHECKBUTTON_LABEL:
     case MOZ_GTK_RADIOBUTTON_LABEL:
     case MOZ_GTK_SPLITTER_HORIZONTAL:
     case MOZ_GTK_SPLITTER_VERTICAL:
     case MOZ_GTK_CHECKBUTTON: