Set the chromehidden attribute earlier, so we don't have to reresolve style and

redo layout on the whole window.  Bug 345560, r=sicking, sr=neil.

content/xul/document/src/Makefile.in

@@ -70,6 +70,7 @@ REQUIRES	= xpcom \
 		  xultmpl \
 		  webshell \
 		  unicharutil \
+		  appshell \
 		  $(NULL)
 
 CPPSRCS		= nsXULControllers.cpp

content/xul/document/src/nsXULDocument.cpp

@@ -122,6 +122,9 @@
 #include "nsContentErrors.h"
 #include "nsIObserverService.h"
 #include "nsNodeUtils.h"
+#include "nsIDocShellTreeItem.h"
+#include "nsIDocShellTreeOwner.h"
+#include "nsIXULWindow.h"
 
 //----------------------------------------------------------------------
 //
@@ -2940,6 +2943,25 @@ nsXULDocument::ResumeWalk()
         }
         SetTitle(title);
 
+        // Before starting layout, check whether we're a toplevel chrome
+        // window.  If we are, set our chrome flags now, so that we don't have
+        // to restyle the whole frame tree after StartLayout.
+        nsCOMPtr<nsISupports> container = GetContainer();
+        nsCOMPtr<nsIDocShellTreeItem> item = do_QueryInterface(container);
+        if (item) {
+            nsCOMPtr<nsIDocShellTreeOwner> owner;
+            item->GetTreeOwner(getter_AddRefs(owner));
+            nsCOMPtr<nsIXULWindow> xulWin = do_GetInterface(owner);
+            if (xulWin) {
+                nsCOMPtr<nsIDocShell> xulWinShell;
+                xulWin->GetDocShell(getter_AddRefs(xulWinShell));
+                if (SameCOMIdentity(xulWinShell, container)) {
+                    // We're the chrome document!  Apply our chrome flags now.
+                    xulWin->ApplyChromeFlags();
+                }
+            }
+        }
+
         StartLayout();
 
         if (mIsWritingFastLoad && IsChromeURI(mDocumentURI))

xpfe/appshell/public/nsIXULWindow.idl

@@ -138,4 +138,12 @@ interface nsIXULWindow : nsISupports
                                in nsIAppShell aAppShell);
 
   attribute nsIXULBrowserWindow XULBrowserWindow;
+
+  /**
+   * Back-door method to force application of chrome flags at a particular
+   * time.  Do NOT call this unless you know what you're doing!  In particular,
+   * calling this when this XUL window doesn't yet have a document in its
+   * docshell could cause problems.
+   */
+  [noscript] void applyChromeFlags();
 };

xpfe/appshell/src/nsXULWindow.cpp

@@ -2012,20 +2012,27 @@ void nsXULWindow::PersistentAttributesDirty(PRUint32 aDirtyFlags)
   mPersistentAttributesDirty |= aDirtyFlags & mPersistentAttributesMask;
 }
 
-nsresult nsXULWindow::ApplyChromeFlags()
+NS_IMETHODIMP nsXULWindow::ApplyChromeFlags()
 {
   nsCOMPtr<nsIDOMElement> window;
   GetWindowDOMElement(getter_AddRefs(window));
   NS_ENSURE_TRUE(window, NS_ERROR_FAILURE);
 
-  // menubar has its own special treatment
-  mWindow->ShowMenuBar(mChromeFlags & nsIWebBrowserChrome::CHROME_MENUBAR ? 
-                       PR_TRUE : PR_FALSE);
+  if (mChromeLoaded) {
+    // The two calls in this block don't need to happen early because they
+    // don't cause a global restyle on the document.  Not only that, but the
+    // scrollbar stuff needs a content area to toggle the scrollbars on anyway.
+    // So just don't do these until mChromeLoaded is true.
+    
+    // menubar has its own special treatment
+    mWindow->ShowMenuBar(mChromeFlags & nsIWebBrowserChrome::CHROME_MENUBAR ? 
+                         PR_TRUE : PR_FALSE);
 
-  // Scrollbars have their own special treatment.
-  SetContentScrollbarVisibility(mChromeFlags &
+    // Scrollbars have their own special treatment.
+    SetContentScrollbarVisibility(mChromeFlags &
                                   nsIWebBrowserChrome::CHROME_SCROLLBARS ?
-                                PR_TRUE : PR_FALSE);
+                                    PR_TRUE : PR_FALSE);
+  }
 
   /* the other flags are handled together. we have style rules
      in navigator.css that trigger visibility based on
@@ -2050,14 +2057,9 @@ nsresult nsXULWindow::ApplyChromeFlags()
   if (! (mChromeFlags & nsIWebBrowserChrome::CHROME_EXTRA))
     newvalue.AppendLiteral("extrachrome ");
 
-
-  // Get the old value, to avoid useless style reflows if we're just
-  // setting stuff to the exact same thing.
-  nsAutoString oldvalue;
-  window->GetAttribute(NS_LITERAL_STRING("chromehidden"), oldvalue);
-
-  if (oldvalue != newvalue)
-    window->SetAttribute(NS_LITERAL_STRING("chromehidden"), newvalue);
+  // Note that if we're not actually changing the value this will be a no-op,
+  // so no need to compare to the old value.
+  window->SetAttribute(NS_LITERAL_STRING("chromehidden"), newvalue);
 
   return NS_OK;
 }

xpfe/appshell/src/nsXULWindow.h

@@ -148,7 +148,6 @@ protected:
    void       SetContentScrollbarVisibility(PRBool aVisible);
    PRBool     GetContentScrollbarVisibility();
    void       PersistentAttributesDirty(PRUint32 aDirtyFlags);
-   nsresult   ApplyChromeFlags();
 
    nsChromeTreeOwner*      mChromeTreeOwner;
    nsContentTreeOwner*     mContentTreeOwner;