Add a faster method for iterating the nsIContent children of an

nsINode if we know that there will be no DOM mutations of any sort
during the iteration.  Bug 429744, r+sr=jst

content/base/public/nsINode.h

@@ -148,8 +148,9 @@ inline nsINode* NODE_FROM(C& aContent, D& aDocument)
 
 // IID for the nsINode interface
 #define NS_INODE_IID \
-{ 0x6f69dd90, 0x318d, 0x40ac, \
-  { 0xb8, 0xb8, 0x99, 0xb8, 0xa7, 0xbb, 0x9a, 0x58 } }
+{ 0x2593b0d5, 0x9a06, 0x4d6b, \
+  { 0x9a, 0x10, 0xb1, 0x39, 0x9f, 0x1b, 0xa0, 0x8e } }
+
 
 /**
  * An internal interface that abstracts some DOMNode-related parts that both
@@ -233,6 +234,16 @@ public:
    */
   virtual nsIContent* GetChildAt(PRUint32 aIndex) const = 0;
 
+  /**
+   * Get a raw pointer to the child array.  This should only be used if you
+   * plan to walk a bunch of the kids, promise to make sure that nothing ever
+   * mutates (no attribute changes, not DOM tree changes, no script execution,
+   * NOTHING), and will never ever peform an out-of-bounds access here.  This
+   * method may return null if there are no children, or it may return a
+   * garbage pointer..
+   */
+  virtual nsIContent * const * GetChildArray() const = 0;
+
   /**
    * Get the index of a child within this content
    * @param aPossibleChild the child to get the index of.

content/base/src/nsAttrAndChildArray.cpp

@@ -145,6 +145,16 @@ nsAttrAndChildArray::GetSafeChildAt(PRUint32 aPos) const
   return nsnull;
 }
 
+nsIContent * const *
+nsAttrAndChildArray::GetChildArray() const
+{
+  if (!mImpl) {
+    return nsnull;
+  }
+  
+  return reinterpret_cast<nsIContent**>(mImpl->mBuffer + AttrSlotsSize());
+}
+
 nsresult
 nsAttrAndChildArray::InsertChildAt(nsIContent* aChild, PRUint32 aPos)
 {

content/base/src/nsAttrAndChildArray.h

@@ -88,6 +88,7 @@ public:
     return reinterpret_cast<nsIContent*>(mImpl->mBuffer[AttrSlotsSize() + aPos]);
   }
   nsIContent* GetSafeChildAt(PRUint32 aPos) const;
+  nsIContent * const * GetChildArray() const;
   nsresult AppendChild(nsIContent* aChild)
   {
     return InsertChildAt(aChild, ChildCount());

content/base/src/nsDOMAttribute.cpp

@@ -64,7 +64,7 @@ PRBool nsDOMAttribute::sInitialized;
 nsDOMAttribute::nsDOMAttribute(nsDOMAttributeMap *aAttrMap,
                                nsINodeInfo       *aNodeInfo,
                                const nsAString   &aValue)
-  : nsIAttribute(aAttrMap, aNodeInfo), mValue(aValue)
+  : nsIAttribute(aAttrMap, aNodeInfo), mValue(aValue), mChild(nsnull)
 {
   NS_ABORT_IF_FALSE(mNodeInfo, "We must get a nodeinfo here!");
 
@@ -73,18 +73,23 @@ nsDOMAttribute::nsDOMAttribute(nsDOMAttributeMap *aAttrMap,
   // to drop our reference when it goes away.
 }
 
+nsDOMAttribute::~nsDOMAttribute()
+{
+  NS_IF_RELEASE(mChild);
+}
+
 NS_IMPL_CYCLE_COLLECTION_CLASS(nsDOMAttribute)
 
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(nsDOMAttribute)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE_NSCOMPTR(mNodeInfo)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_NSCOMPTR(mChild)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_RAWPTR(mChild)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE_LISTENERMANAGER
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE_USERDATA
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE_PRESERVED_WRAPPER
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsDOMAttribute)
-  NS_IMPL_CYCLE_COLLECTION_UNLINK_NSCOMPTR(mChild)
+  NS_IF_RELEASE(tmp->mChild);
   NS_IMPL_CYCLE_COLLECTION_UNLINK_LISTENERMANAGER
   NS_IMPL_CYCLE_COLLECTION_UNLINK_USERDATA
   NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER
@@ -668,8 +673,14 @@ nsDOMAttribute::GetChildAt(PRUint32 aIndex) const
   PRBool hasChild;
   EnsureChildState(PR_TRUE, hasChild);
 
-  return aIndex == 0 && hasChild ? mChild.get() : nsnull;
+  return aIndex == 0 && hasChild ? mChild : nsnull;
 }
+
+nsIContent * const *
+nsDOMAttribute::GetChildArray() const
+{
+  return &mChild;
+}  
   
 PRInt32
 nsDOMAttribute::IndexOf(nsINode* aPossibleChild) const
@@ -779,7 +790,7 @@ nsDOMAttribute::EnsureChildState(PRBool aSetText, PRBool &aHasChild) const
   mutableThis->GetValue(value);
 
   if (!mChild && !value.IsEmpty()) {
-    nsresult rv = NS_NewTextNode(getter_AddRefs(mutableThis->mChild),
+    nsresult rv = NS_NewTextNode(&mutableThis->mChild,
                                  mNodeInfo->NodeInfoManager());
     NS_ENSURE_SUCCESS(rv, rv);
 

content/base/src/nsDOMAttribute.h

@@ -66,6 +66,7 @@ class nsDOMAttribute : public nsIAttribute,
 public:
   nsDOMAttribute(nsDOMAttributeMap* aAttrMap, nsINodeInfo *aNodeInfo,
                  const nsAString& aValue);
+  virtual ~nsDOMAttribute();
 
   NS_DECL_CYCLE_COLLECTING_ISUPPORTS
 
@@ -90,6 +91,7 @@ public:
   virtual PRBool IsNodeOfType(PRUint32 aFlags) const;
   virtual PRUint32 GetChildCount() const;
   virtual nsIContent *GetChildAt(PRUint32 aIndex) const;
+  virtual nsIContent * const * GetChildArray() const;
   virtual PRInt32 IndexOf(nsINode* aPossibleChild) const;
   virtual nsresult InsertChildAt(nsIContent* aKid, PRUint32 aIndex,
                                  PRBool aNotify);
@@ -121,9 +123,10 @@ private:
   nsresult EnsureChildState(PRBool aSetText, PRBool &aHasChild) const;
 
   nsString mValue;
-  // XXX For now, there's only a single child - a text
-  // element representing the value
-  nsCOMPtr<nsIContent> mChild;
+  // XXX For now, there's only a single child - a text element
+  // representing the value.  This is strong ref, but we use a raw
+  // pointer so we can implement GetChildArray().
+  nsIContent* mChild;
 
   nsIContent *GetContentInternal() const
   {

content/base/src/nsDocument.cpp

@@ -2682,6 +2682,13 @@ nsDocument::GetChildCount() const
   return mChildren.ChildCount();
 }
 
+nsIContent * const *
+nsDocument::GetChildArray() const
+{
+  return mChildren.GetChildArray();
+}
+  
+
 nsresult
 nsDocument::InsertChildAt(nsIContent* aKid, PRUint32 aIndex,
                           PRBool aNotify)

content/base/src/nsDocument.h

@@ -630,6 +630,7 @@ public:
   // nsINode
   virtual PRBool IsNodeOfType(PRUint32 aFlags) const;
   virtual nsIContent *GetChildAt(PRUint32 aIndex) const;
+  virtual nsIContent * const * GetChildArray() const;
   virtual PRInt32 IndexOf(nsINode* aPossibleChild) const;
   virtual PRUint32 GetChildCount() const;
   virtual nsresult InsertChildAt(nsIContent* aKid, PRUint32 aIndex,

content/base/src/nsGenericDOMDataNode.cpp

@@ -800,6 +800,12 @@ nsGenericDOMDataNode::GetChildAt(PRUint32 aIndex) const
   return nsnull;
 }
 
+nsIContent * const *
+nsGenericDOMDataNode::GetChildArray() const
+{
+  return nsnull;
+}
+
 PRInt32
 nsGenericDOMDataNode::IndexOf(nsINode* aPossibleChild) const
 {

content/base/src/nsGenericDOMDataNode.h

@@ -172,6 +172,7 @@ public:
   // nsINode methods
   virtual PRUint32 GetChildCount() const;
   virtual nsIContent *GetChildAt(PRUint32 aIndex) const;
+  virtual nsIContent * const * GetChildArray() const;
   virtual PRInt32 IndexOf(nsINode* aPossibleChild) const;
   virtual nsresult InsertChildAt(nsIContent* aKid, PRUint32 aIndex,
                                  PRBool aNotify);

content/base/src/nsGenericElement.cpp

@@ -4322,6 +4322,12 @@ nsGenericElement::GetChildAt(PRUint32 aIndex) const
   return mAttrsAndChildren.GetSafeChildAt(aIndex);
 }
 
+nsIContent * const *
+nsGenericElement::GetChildArray() const
+{
+  return mAttrsAndChildren.GetChildArray();
+}
+
 PRInt32
 nsGenericElement::IndexOf(nsINode* aPossibleChild) const
 {

content/base/src/nsGenericElement.h

@@ -361,6 +361,7 @@ public:
   // nsINode interface methods
   virtual PRUint32 GetChildCount() const;
   virtual nsIContent *GetChildAt(PRUint32 aIndex) const;
+  virtual nsIContent * const * GetChildArray() const;
   virtual PRInt32 IndexOf(nsINode* aPossibleChild) const;
   virtual nsresult InsertChildAt(nsIContent* aKid, PRUint32 aIndex,
                                  PRBool aNotify);

content/xul/content/src/nsXULElement.cpp

@@ -947,6 +947,16 @@ nsXULElement::GetChildAt(PRUint32 aIndex) const
     return mAttrsAndChildren.GetSafeChildAt(aIndex);
 }
 
+nsIContent * const *
+nsXULElement::GetChildArray() const
+{
+    if (NS_FAILED(EnsureContentsGenerated())) {
+        return nsnull;
+    }
+
+    return mAttrsAndChildren.GetChildArray();
+}
+
 PRInt32
 nsXULElement::IndexOf(nsINode* aPossibleChild) const
 {

content/xul/content/src/nsXULElement.h

@@ -543,6 +543,7 @@ public:
     // nsINode
     virtual PRUint32 GetChildCount() const;
     virtual nsIContent *GetChildAt(PRUint32 aIndex) const;
+    virtual nsIContent * const * GetChildArray() const;
     virtual PRInt32 IndexOf(nsINode* aPossibleChild) const;
     virtual nsresult PreHandleEvent(nsEventChainPreVisitor& aVisitor);
     virtual nsresult InsertChildAt(nsIContent* aKid, PRUint32 aIndex,