--- a/browser/base/content/browser-tabsintitlebar.js
+++ b/browser/base/content/browser-tabsintitlebar.js
@@ -143,23 +143,29 @@ var TabsInTitlebar = {
     let menubar = $("toolbar-menubar");
 
     if (allowed) {
       // We set the tabsintitlebar attribute first so that our CSS for
       // tabsintitlebar manifests before we do our measurements.
       document.documentElement.setAttribute("tabsintitlebar", "true");
       updateTitlebarDisplay();
 
+      // Reset the custom titlebar height if the menubar is shown,
+      // because we will want to calculate its original height.
+      if (AppConstants.isPlatformAndVersionAtLeast("win", "10.0") &&
+          (menubar.getAttribute("inactive") != "true" ||
+          menubar.getAttribute("autohide") != "true")) {
+        $("titlebar-buttonbox").style.removeProperty("height");
+      }
+
       // Try to avoid reflows in this code by calculating dimensions first and
       // then later set the properties affecting layout together in a batch.
 
-      // Get the full height of the tabs toolbar:
-      let tabsToolbar = $("TabsToolbar");
-      let tabsStyles = window.getComputedStyle(tabsToolbar);
-      let fullTabsHeight = rect(tabsToolbar).height + verticalMargins(tabsStyles);
+      // Get the height of the tabs toolbar:
+      let tabsHeight = rect($("TabsToolbar")).height;
       // Buttons first:
       let captionButtonsBoxWidth = rect($("titlebar-buttonbox-container")).width;
 
       let secondaryButtonsWidth, menuHeight, fullMenuHeight, menuStyles;
       if (AppConstants.platform == "macosx") {
         secondaryButtonsWidth = rect($("titlebar-secondary-buttonbox")).width;
         // No need to look up the menubar stuff on OS X:
         menuHeight = 0;
@@ -171,22 +177,22 @@ var TabsInTitlebar = {
         fullMenuHeight = verticalMargins(menuStyles) + menuHeight;
       }
 
       // And get the height of what's in the titlebar:
       let titlebarContentHeight = rect(titlebarContent).height;
 
       // Begin setting CSS properties which will cause a reflow
 
+      // On Windows 10, adjust the window controls to span the entire
+      // tab strip height if we're not showing a menu bar.
       if (AppConstants.isPlatformAndVersionAtLeast("win", "10.0")) {
-        if (!menuHeight && window.windowState == window.STATE_MAXIMIZED) {
-          titlebarContentHeight = Math.max(titlebarContentHeight, fullTabsHeight);
+        if (!menuHeight) {
+          titlebarContentHeight = tabsHeight;
           $("titlebar-buttonbox").style.height = titlebarContentHeight + "px";
-        } else {
-          $("titlebar-buttonbox").style.removeProperty("height");
         }
       }
 
       // If the menubar is around (menuHeight is non-zero), try to adjust
       // its full height (i.e. including margins) to match the titlebar,
       // by changing the menubar's bottom padding
       if (menuHeight) {
         // Calculate the difference between the titlebar's height and that of the menubar
@@ -209,17 +215,17 @@ var TabsInTitlebar = {
           menubar.style.paddingBottom = desiredPadding + "px";
           // We've changed the menu height now:
           fullMenuHeight += desiredPadding - existingPadding;
         }
       }
 
       // 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;
+      let tabAndMenuHeight = tabsHeight + 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") {
           titlebarContent.style.marginBottom = extraMargin + "px";
         }

--- a/browser/base/content/test/performance/browser_windowopen_reflows.js
+++ b/browser/base/content/test/performance/browser_windowopen_reflows.js
@@ -84,26 +84,16 @@ if (Services.appinfo.OS == "WINNT" || Se
       stack: [
         "rect@chrome://browser/content/browser-tabsintitlebar.js",
         "_update@chrome://browser/content/browser-tabsintitlebar.js",
         "init@chrome://browser/content/browser-tabsintitlebar.js",
         "handleEvent@chrome://browser/content/tabbrowser.xml",
       ],
       times: 4, // This number should only ever go down - never up.
     },
-
-    {
-      stack: [
-        "verticalMargins@chrome://browser/content/browser-tabsintitlebar.js",
-        "_update@chrome://browser/content/browser-tabsintitlebar.js",
-        "init@chrome://browser/content/browser-tabsintitlebar.js",
-        "handleEvent@chrome://browser/content/tabbrowser.xml",
-      ],
-      times: 2, // This number should only ever go down - never up.
-    }
   );
 }
 
 /*
  * This test ensures that there are no unexpected
  * uninterruptible reflows when opening new windows.
  */
 add_task(async function() {

--- a/browser/themes/windows/browser-aero.css
+++ b/browser/themes/windows/browser-aero.css
@@ -2,19 +2,21 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 %filter substitution
 %define toolbarShadowColor hsla(209,67%,12%,0.35)
 %define glassActiveBorderColor rgb(37, 44, 51)
 %define glassInactiveBorderColor rgb(102, 102, 102)
 
-@media not all and (-moz-windows-classic) {
-  #main-window[sizemode="normal"] > #tab-view-deck > #browser-panel > #navigator-toolbox > #toolbar-menubar {
-    margin-top: 1px;
+@media (-moz-os-version: windows-win7) {
+  @media not all and (-moz-windows-classic) {
+    #main-window[sizemode="normal"] > #tab-view-deck > #browser-panel > #navigator-toolbox > #toolbar-menubar {
+      margin-top: 1px;
+    }
   }
 }
 
 @media (-moz-windows-default-theme) {
   .sidebar-header,
   #sidebar-header {
     -moz-appearance: none;
     border-bottom: none;
@@ -76,26 +78,21 @@
       #titlebar-buttonbox,
       .titlebar-button {
         -moz-appearance: none !important;
       }
 
       .titlebar-button {
         border: none;
         margin: 0 !important;
-        padding: 10px 17px;
+        padding: 8px 17px;
         -moz-context-properties: stroke;
         stroke: var(--titlebar-text-color);
       }
 
-      :root[sizemode=maximized] .titlebar-button {
-        padding-top: 8px;
-        padding-bottom: 8px;
-      }
-
       .titlebar-button > .toolbarbutton-icon {
         width: 12px;
         height: 12px;
       }
 
       #titlebar-min {
         list-style-image: url(chrome://browser/skin/window-controls/minimize.svg);
       }