Bug 1930292 - Stop setting non-zero chromemargin values. r=win-reviewers,handyman

These only do something on Windows, and after windows 7 they are not
useful at all.

If this has no fallout I plan to simplify the code further in a
follow-up (we can basically make this a boolean attribute again or so).

Differential Revision: https://phabricator.services.mozilla.com/D228528

browser/base/content/browser-tabsintitlebar.js

@@ -69,11 +69,9 @@ var TabsInTitlebar = {
       !Object.keys(this._disallowed).length;
     if (allowed) {
       document.documentElement.setAttribute("tabsintitlebar", "true");
+      document.documentElement.setAttribute("chromemargin", "0,0,0,0");
       if (AppConstants.platform == "macosx") {
-        document.documentElement.setAttribute("chromemargin", "0,-1,-1,-1");
         document.documentElement.removeAttribute("drawtitle");
-      } else {
-        document.documentElement.setAttribute("chromemargin", "0,2,2,2");
       }
     } else {
       document.documentElement.removeAttribute("tabsintitlebar");

browser/base/content/browser.xhtml

@@ -17,11 +17,7 @@
 #endif
         data-l10n-args="{"content-title":"CONTENTTITLE"}"
         data-l10n-attrs="data-content-title-default, data-content-title-private, data-title-default, data-title-private"
-#ifdef XP_WIN
+        chromemargin="0,0,0,0"
-        chromemargin="0,2,2,2"
-#else
-        chromemargin="0,-1,-1,-1"
-#endif
         tabsintitlebar="true"
         windowtype="navigator:browser"
         macanimationtype="document"

mozglue/misc/PreXULSkeletonUI.cpp

@@ -1995,22 +1995,16 @@ static Result<Ok, PreXULSkeletonUIError> CreateAndStorePreXULSkeletonUIImpl(
   sCaptionHeight =
       sVerticalResizeMargin + sGetSystemMetricsForDpi(SM_CYCAPTION, sDpi);
 
-  // These match the margins set in browser-tabsintitlebar.js with default prefs
+  // These match the offsets that we get with default prefs. We don't use the
-  // on Windows. We don't use the skeleton ui if tabsInTitlebar is disabled, see
+  // skeleton ui if tabsInTitlebar is disabled, see bug 1673092.
-  // bug 1673092.
-  const Margin nonClientMargin{0, 2, 2, 2};
-
   if (sMaximized) {
     sNonClientOffset.top = sCaptionHeight - sVerticalResizeMargin;
   } else {
     // See nsWindow::NormalWindowNonClientOffset()
     sNonClientOffset.top = sCaptionHeight;
-    sNonClientOffset.bottom =
+    sNonClientOffset.bottom = sVerticalResizeMargin;
-        std::min(sVerticalResizeMargin, nonClientMargin.bottom);
+    sNonClientOffset.left = sHorizontalResizeMargin;
-    sNonClientOffset.left =
+    sNonClientOffset.right = sHorizontalResizeMargin;
-        std::min(sHorizontalResizeMargin, nonClientMargin.left);
-    sNonClientOffset.right =
-        std::min(sHorizontalResizeMargin, nonClientMargin.right);
   }
 
   if (sMaximized) {

toolkit/content/tests/chrome/window_maximized_persist_with_no_titlebar.xhtml

@@ -5,7 +5,7 @@
         height="300"
         width="300"
         sizemode="normal"
-        chromemargin="0,2,2,2"
+        chromemargin="0,0,0,0"
         id="window"
         persist="height width sizemode">
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