Call BeginUpdate before going into the guts of updating a style attribute so that the resulting flush happens sooner. (Bug 522595) r=bzbarsky

layout/style/nsCSSStyleRule.cpp

@@ -916,6 +916,7 @@ public:
                                             nsICSSLoader** aCSSLoader,
                                             nsICSSParser** aCSSParser);
   virtual nsresult DeclarationChanged();
+  virtual nsIDocument* DocToUpdate();
 
   // Override |AddRef| and |Release| for being a member of
   // |DOMCSSStyleRuleImpl|.
@@ -1109,6 +1110,12 @@ DOMCSSDeclarationImpl::DeclarationChanged()
   return NS_OK;
 }
 
+nsIDocument*
+DOMCSSDeclarationImpl::DocToUpdate()
+{
+  return nsnull;
+}
+
 DOMCSSStyleRuleImpl::DOMCSSStyleRuleImpl(nsICSSStyleRule* aRule)
   : mDOMDeclaration(aRule)
 {

layout/style/nsDOMCSSAttrDeclaration.cpp

@@ -105,6 +105,14 @@ nsDOMCSSAttributeDeclaration::DeclarationChanged()
     mContent->SetInlineStyleRule(newRule, PR_TRUE);
 }
 
+nsIDocument*
+nsDOMCSSAttributeDeclaration::DocToUpdate()
+{
+  // We need GetOwnerDoc() rather than GetCurrentDoc() because it might
+  // be the BeginUpdate call that inserts mContent into the document.
+  return mContent->GetOwnerDoc();
+}
+
 nsresult
 nsDOMCSSAttributeDeclaration::GetCSSDeclaration(nsCSSDeclaration **aDecl,
                                                 PRBool aAllocate)

layout/style/nsDOMCSSAttrDeclaration.h

@@ -81,6 +81,7 @@ public:
 
 protected:
   virtual nsresult DeclarationChanged();
+  virtual nsIDocument* DocToUpdate();
   
   nsCOMPtr<nsIContent> mContent;
 

layout/style/nsDOMCSSDeclaration.cpp

@@ -51,6 +51,7 @@
 #include "nsIPrincipal.h"
 
 #include "nsContentUtils.h"
+#include "mozAutoDocUpdate.h"
 
 
 nsDOMCSSDeclaration::~nsDOMCSSDeclaration()
@@ -263,6 +264,13 @@ nsDOMCSSDeclaration::ParsePropertyValue(const nsCSSProperty aPropID,
     return result;
   }
 
+  // For nsDOMCSSAttributeDeclaration, DeclarationChanged will lead to
+  // Attribute setting code, which leads in turn to BeginUpdate.  We
+  // need to start the update now so that the old rule doesn't get used
+  // between when we mutate the declaration and when we set the new
+  // rule (see stack in bug 209575).
+  mozAutoDocConditionalContentUpdateBatch autoUpdate(DocToUpdate(), PR_TRUE);
+
   PRBool changed;
   result = cssParser->ParseProperty(aPropID, aPropValue, sheetURI, baseURI,
                                     sheetPrincipal, decl, &changed);
@@ -303,6 +311,13 @@ nsDOMCSSDeclaration::ParseDeclaration(const nsAString& aDecl,
     return result;
   }
 
+  // For nsDOMCSSAttributeDeclaration, DeclarationChanged will lead to
+  // Attribute setting code, which leads in turn to BeginUpdate.  We
+  // need to start the update now so that the old rule doesn't get used
+  // between when we mutate the declaration and when we set the new
+  // rule (see stack in bug 209575).
+  mozAutoDocConditionalContentUpdateBatch autoUpdate(DocToUpdate(), PR_TRUE);
+
   PRBool changed;
   result = cssParser->ParseAndAppendDeclaration(aDecl, sheetURI, baseURI,
                                                 sheetPrincipal, decl,
@@ -330,6 +345,13 @@ nsDOMCSSDeclaration::RemoveProperty(const nsCSSProperty aPropID)
     return rv;
   }
 
+  // For nsDOMCSSAttributeDeclaration, DeclarationChanged will lead to
+  // Attribute setting code, which leads in turn to BeginUpdate.  We
+  // need to start the update now so that the old rule doesn't get used
+  // between when we mutate the declaration and when we set the new
+  // rule (see stack in bug 209575).
+  mozAutoDocConditionalContentUpdateBatch autoUpdate(DocToUpdate(), PR_TRUE);
+
   rv = decl->RemoveProperty(aPropID);
 
   if (NS_SUCCEEDED(rv)) {

layout/style/nsDOMCSSDeclaration.h

@@ -50,6 +50,7 @@ class nsICSSParser;
 class nsICSSLoader;
 class nsIURI;
 class nsIPrincipal;
+class nsIDocument;
 
 class CSS2PropertiesTearoff : public nsIDOMNSCSS2Properties
 {
@@ -101,6 +102,10 @@ protected:
   virtual nsresult GetCSSDeclaration(nsCSSDeclaration **aDecl,
                                      PRBool aAllocate) = 0;
   virtual nsresult DeclarationChanged() = 0;
+  // Document that we must call BeginUpdate/EndUpdate on around the
+  // calls to DeclarationChanged and the style rule mutation that leads
+  // to it.
+  virtual nsIDocument* DocToUpdate() = 0;
   
   // This will only fail if it can't get a parser or a principal.
   // This means it can return NS_OK without aURI or aCSSLoader being